diff --git a/CHANGELOG.md b/CHANGELOG.md
index c2cbc38b0..7144ab2f1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,6 @@
 ## v0.10.2
 
-  - Change the HTTP framework, moving from tide to actix-web #601
+  - Change the HTTP framework, moving from tide to actix-web (#601)
   - Bump sentry version to 0.18.1 (#690)
   - Enable max payload size override (#684)
   - Disable sentry in debug (#681)
@@ -18,6 +18,7 @@
   - Update sentry features to remove openssl (#702)
   - Add SSL support (#669)
   - Rename fieldsFrequency into fieldsDistribution in stats (#719)
+  - Add support for error code reporting (#703)
 
 ## v0.10.1
 
diff --git a/Cargo.lock b/Cargo.lock
index a2b38b19a..ea62dfe64 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1653,6 +1653,7 @@ dependencies = [
  "jemallocator",
  "levenshtein_automata",
  "log",
+ "meilisearch-error",
  "meilisearch-schema",
  "meilisearch-tokenizer",
  "meilisearch-types",
@@ -1673,6 +1674,13 @@ dependencies = [
  "zerocopy",
 ]
 
+[[package]]
+name = "meilisearch-error"
+version = "0.10.1"
+dependencies = [
+ "actix-http",
+]
+
 [[package]]
 name = "meilisearch-http"
 version = "0.10.1"
@@ -1690,7 +1698,6 @@ dependencies = [
  "crossbeam-channel",
  "env_logger",
  "futures",
- "heed",
  "http 0.1.21",
  "http-service",
  "http-service-mock",
@@ -1699,6 +1706,7 @@ dependencies = [
  "log",
  "main_error",
  "meilisearch-core",
+ "meilisearch-error",
  "meilisearch-schema",
  "meilisearch-tokenizer",
  "mime",
@@ -1729,6 +1737,7 @@ version = "0.10.1"
 dependencies = [
  "bincode",
  "indexmap",
+ "meilisearch-error",
  "serde",
  "serde_json",
  "toml",
diff --git a/meilisearch-core/Cargo.toml b/meilisearch-core/Cargo.toml
index 912210007..4d092d8af 100644
--- a/meilisearch-core/Cargo.toml
+++ b/meilisearch-core/Cargo.toml
@@ -24,6 +24,7 @@ intervaltree = "0.2.5"
 itertools = "0.9.0"
 levenshtein_automata = { version = "0.2.0", features = ["fst_automaton"] }
 log = "0.4.8"
+meilisearch-error = { path = "../meilisearch-error", version = "0.10.1" }
 meilisearch-schema = { path = "../meilisearch-schema", version = "0.10.1" }
 meilisearch-tokenizer = { path = "../meilisearch-tokenizer", version = "0.10.1" }
 meilisearch-types = { path = "../meilisearch-types", version = "0.10.1" }
diff --git a/meilisearch-core/examples/from_file.rs b/meilisearch-core/examples/from_file.rs
index 821f23fcc..af41efb6c 100644
--- a/meilisearch-core/examples/from_file.rs
+++ b/meilisearch-core/examples/from_file.rs
@@ -126,9 +126,7 @@ fn index_command(command: IndexCommand, database: Database) -> Result<(), Box<dy
         settings.into_update().unwrap()
     };
 
-    let mut update_writer = db.update_write_txn().unwrap();
-    index.settings_update(&mut update_writer, settings)?;
-    update_writer.commit().unwrap();
+    db.update_write(|w| index.settings_update(w, settings))?;
 
     let mut rdr = if command.csv_data_path.as_os_str() == "-" {
         csv::Reader::from_reader(Box::new(io::stdin()) as Box<dyn Read>)
@@ -175,10 +173,9 @@ fn index_command(command: IndexCommand, database: Database) -> Result<(), Box<dy
 
         println!();
 
-        let mut update_writer = db.update_write_txn().unwrap();
+        let update_id = db.update_write(|w| additions.finalize(w))?;
+
         println!("committing update...");
-        let update_id = additions.finalize(&mut update_writer)?;
-        update_writer.commit().unwrap();
         max_update_id = max_update_id.max(update_id);
         println!("committed update {}", update_id);
     }
diff --git a/meilisearch-core/src/database.rs b/meilisearch-core/src/database.rs
index a26324930..79a1e430c 100644
--- a/meilisearch-core/src/database.rs
+++ b/meilisearch-core/src/database.rs
@@ -4,17 +4,30 @@ use std::path::Path;
 use std::sync::{Arc, RwLock};
 use std::{fs, thread};
 
+use chrono::{DateTime, Utc};
 use crossbeam_channel::{Receiver, Sender};
-use heed::types::{Str, Unit};
-use heed::{CompactionOption, Result as ZResult};
-use log::debug;
+use heed::types::{Str, Unit, SerdeBincode};
+use heed::CompactionOption;
+use log::{debug, error};
 use meilisearch_schema::Schema;
 
-use crate::{store, update, Index, MResult};
+use crate::{store, update, Index, MResult, Error};
 
 pub type BoxUpdateFn = Box<dyn Fn(&str, update::ProcessedUpdateResult) + Send + Sync + 'static>;
+
 type ArcSwapFn = arc_swap::ArcSwapOption<BoxUpdateFn>;
 
+type SerdeDatetime = SerdeBincode<DateTime<Utc>>;
+
+pub type MainWriter<'a> = heed::RwTxn<'a, MainT>;
+pub type MainReader = heed::RoTxn<MainT>;
+
+pub type UpdateWriter<'a> = heed::RwTxn<'a, UpdateT>;
+pub type UpdateReader = heed::RoTxn<UpdateT>;
+
+const UNHEALTHY_KEY: &str = "_is_unhealthy";
+const LAST_UPDATE_KEY: &str = "last-update";
+
 pub struct MainT;
 pub struct UpdateT;
 
@@ -241,6 +254,13 @@ impl Database {
         }
     }
 
+    pub fn is_indexing(&self, reader: &UpdateReader, index: &str) -> MResult<Option<bool>> {
+        match self.open_index(&index) {
+            Some(index) => index.current_update_id(&reader).map(|u| Some(u.is_some())),
+            None => Ok(None),
+        }
+    }
+
     pub fn create_index(&self, name: impl AsRef<str>) -> MResult<Index> {
         let name = name.as_ref();
         let mut indexes_lock = self.indexes.write().unwrap();
@@ -319,23 +339,73 @@ impl Database {
         self.update_fn.swap(None);
     }
 
-    pub fn main_read_txn(&self) -> heed::Result<heed::RoTxn<MainT>> {
-        self.env.typed_read_txn::<MainT>()
+    pub fn main_read_txn(&self) -> MResult<MainReader> {
+        Ok(self.env.typed_read_txn::<MainT>()?)
     }
 
-    pub fn main_write_txn(&self) -> heed::Result<heed::RwTxn<MainT>> {
-        self.env.typed_write_txn::<MainT>()
+    pub(crate) fn main_write_txn(&self) -> MResult<MainWriter> {
+        Ok(self.env.typed_write_txn::<MainT>()?)
     }
 
-    pub fn update_read_txn(&self) -> heed::Result<heed::RoTxn<UpdateT>> {
-        self.update_env.typed_read_txn::<UpdateT>()
+    /// Calls f providing it with a writer to the main database. After f is called, makes sure the
+    /// transaction is commited. Returns whatever result f returns.
+    pub fn main_write<F, R, E>(&self, f: F) -> Result<R, E>
+    where
+        F: FnOnce(&mut MainWriter) -> Result<R, E>,
+        E: From<Error>,
+    {
+        let mut writer = self.main_write_txn()?;
+        let result = f(&mut writer)?;
+        writer.commit().map_err(Error::Heed)?;
+        Ok(result)
     }
 
-    pub fn update_write_txn(&self) -> heed::Result<heed::RwTxn<UpdateT>> {
-        self.update_env.typed_write_txn::<UpdateT>()
+    /// provides a context with a reader to the main database. experimental.
+    pub fn main_read<F, R, E>(&self, f: F) -> Result<R, E>
+    where
+        F: FnOnce(&MainReader) -> Result<R, E>,
+        E: From<Error>,
+    {
+        let reader = self.main_read_txn()?;
+        let result = f(&reader)?;
+        reader.abort().map_err(Error::Heed)?;
+        Ok(result)
     }
 
-    pub fn copy_and_compact_to_path<P: AsRef<Path>>(&self, path: P) -> ZResult<(File, File)> {
+    pub fn update_read_txn(&self) -> MResult<UpdateReader> {
+        Ok(self.update_env.typed_read_txn::<UpdateT>()?)
+    }
+
+    pub(crate) fn update_write_txn(&self) -> MResult<heed::RwTxn<UpdateT>> {
+        Ok(self.update_env.typed_write_txn::<UpdateT>()?)
+    }
+
+    /// Calls f providing it with a writer to the main database. After f is called, makes sure the
+    /// transaction is commited. Returns whatever result f returns.
+    pub fn update_write<F, R, E>(&self, f: F) -> Result<R, E>
+    where
+        F: FnOnce(&mut UpdateWriter) -> Result<R, E>,
+        E: From<Error>,
+    {
+        let mut writer = self.update_write_txn()?;
+        let result = f(&mut writer)?;
+        writer.commit().map_err(Error::Heed)?;
+        Ok(result)
+    }
+
+    /// provides a context with a reader to the update database. experimental.
+    pub fn update_read<F, R, E>(&self, f: F) -> Result<R, E>
+    where
+        F: FnOnce(&UpdateReader) -> Result<R, E>,
+        E: From<Error>,
+    {
+        let reader = self.update_read_txn()?;
+        let result = f(&reader)?;
+        reader.abort().map_err(Error::Heed)?;
+        Ok(result)
+    }
+
+    pub fn copy_and_compact_to_path<P: AsRef<Path>>(&self, path: P) -> MResult<(File, File)> {
         let path = path.as_ref();
 
         let env_path = path.join("main");
@@ -352,7 +422,7 @@ impl Database {
             Ok(update_env_file) => Ok((env_file, update_env_file)),
             Err(e) => {
                 fs::remove_file(env_path)?;
-                Err(e)
+                Err(e.into())
             },
         }
     }
@@ -362,9 +432,78 @@ impl Database {
         indexes.keys().cloned().collect()
     }
 
-    pub fn common_store(&self) -> heed::PolyDatabase {
+    pub(crate) fn common_store(&self) -> heed::PolyDatabase {
         self.common_store
     }
+
+    pub fn last_update(&self, reader: &heed::RoTxn<MainT>) -> MResult<Option<DateTime<Utc>>> {
+        match self.common_store()
+            .get::<_, Str, SerdeDatetime>(reader, LAST_UPDATE_KEY)? {
+                Some(datetime) => Ok(Some(datetime)),
+                None => Ok(None),
+            }
+    }
+
+    pub fn set_last_update(&self, writer: &mut heed::RwTxn<MainT>, time: &DateTime<Utc>) -> MResult<()> {
+        self.common_store()
+            .put::<_, Str, SerdeDatetime>(writer, LAST_UPDATE_KEY, time)?;
+        Ok(())
+    }
+
+    pub fn set_healthy(&self, writer: &mut heed::RwTxn<MainT>) -> MResult<()> {
+        let common_store = self.common_store();
+        common_store.delete::<_, Str>(writer, UNHEALTHY_KEY)?;
+        Ok(())
+    }
+
+    pub fn set_unhealthy(&self, writer: &mut heed::RwTxn<MainT>) -> MResult<()> {
+        let common_store = self.common_store();
+        common_store.put::<_, Str, Unit>(writer, UNHEALTHY_KEY, &())?;
+        Ok(())
+    }
+
+    pub fn get_health(&self, reader: &heed::RoTxn<MainT>) -> MResult<Option<()>> {
+        let common_store = self.common_store();
+        Ok(common_store.get::<_, Str, Unit>(&reader, UNHEALTHY_KEY)?)
+    }
+
+    pub fn compute_stats(&self, writer: &mut MainWriter, index_uid: &str) -> MResult<()> {
+        let index = match self.open_index(&index_uid) {
+            Some(index) => index,
+            None => {
+                error!("Impossible to retrieve index {}", index_uid);
+                return Ok(());
+            }
+        };
+
+        let schema = match index.main.schema(&writer)? {
+            Some(schema) => schema,
+            None => return Ok(()),
+        };
+
+        let all_documents_fields = index
+            .documents_fields_counts
+            .all_documents_fields_counts(&writer)?;
+
+        // count fields frequencies
+        let mut fields_frequency = HashMap::<_, usize>::new();
+        for result in all_documents_fields {
+            let (_, attr, _) = result?;
+            if let Some(field_id) = schema.indexed_pos_to_field_id(attr) {
+                *fields_frequency.entry(field_id).or_default() += 1;
+            }
+        }
+
+        // convert attributes to their names
+        let frequency: HashMap<_, _> = fields_frequency
+            .into_iter()
+            .filter_map(|(a, c)| schema.name(a).map(|name| (name.to_string(), c)))
+            .collect();
+
+        index
+            .main
+            .put_fields_distribution(writer, &frequency)
+    }
 }
 
 #[cfg(test)]
diff --git a/meilisearch-core/src/error.rs b/meilisearch-core/src/error.rs
index 7990f691f..62840c2a8 100644
--- a/meilisearch-core/src/error.rs
+++ b/meilisearch-core/src/error.rs
@@ -9,6 +9,8 @@ pub use fst::Error as FstError;
 pub use heed::Error as HeedError;
 pub use pest::error as pest_error;
 
+use meilisearch_error::{ErrorCode, Code};
+
 pub type MResult<T> = Result<T, Error>;
 
 #[derive(Debug)]
@@ -21,17 +23,41 @@ pub enum Error {
     MissingDocumentId,
     MaxFieldsLimitExceeded,
     Schema(meilisearch_schema::Error),
-    Zlmdb(heed::Error),
+    Heed(heed::Error),
     Fst(fst::Error),
     SerdeJson(SerdeJsonError),
     Bincode(bincode::Error),
     Serializer(SerializerError),
     Deserializer(DeserializerError),
-    UnsupportedOperation(UnsupportedOperation),
     FilterParseError(PestError<Rule>),
     FacetError(FacetError),
 }
 
+impl ErrorCode for Error {
+    fn error_code(&self) -> Code {
+        use Error::*;
+
+        match self {
+            FacetError(_) => Code::Facet,
+            FilterParseError(_) => Code::Filter,
+            IndexAlreadyExists => Code::IndexAlreadyExists,
+            MissingPrimaryKey => Code::InvalidState,
+            MissingDocumentId => Code::MissingDocumentId,
+            MaxFieldsLimitExceeded => Code::MaxFieldsLimitExceeded,
+            Schema(s) =>  s.error_code(),
+            WordIndexMissing
+            | SchemaMissing => Code::InvalidState,
+            Heed(_)
+            | Fst(_)
+            | SerdeJson(_)
+            | Bincode(_)
+            | Serializer(_)
+            | Deserializer(_)
+            | Io(_) => Code::Internal,
+        }
+    }
+}
+
 impl From<io::Error> for Error {
     fn from(error: io::Error) -> Error {
         Error::Io(error)
@@ -74,7 +100,7 @@ impl From<meilisearch_schema::Error> for Error {
 
 impl From<HeedError> for Error {
     fn from(error: HeedError) -> Error {
-        Error::Zlmdb(error)
+        Error::Heed(error)
     }
 }
 
@@ -108,12 +134,6 @@ impl From<DeserializerError> for Error {
     }
 }
 
-impl From<UnsupportedOperation> for Error {
-    fn from(op: UnsupportedOperation) -> Error {
-        Error::UnsupportedOperation(op)
-    }
-}
-
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         use self::Error::*;
@@ -126,13 +146,12 @@ impl fmt::Display for Error {
             MissingDocumentId => write!(f, "document id is missing"),
             MaxFieldsLimitExceeded => write!(f, "maximum number of fields in a document exceeded"),
             Schema(e) => write!(f, "schema error; {}", e),
-            Zlmdb(e) => write!(f, "heed error; {}", e),
+            Heed(e) => write!(f, "heed error; {}", e),
             Fst(e) => write!(f, "fst error; {}", e),
             SerdeJson(e) => write!(f, "serde json error; {}", e),
             Bincode(e) => write!(f, "bincode error; {}", e),
             Serializer(e) => write!(f, "serializer error; {}", e),
             Deserializer(e) => write!(f, "deserializer error; {}", e),
-            UnsupportedOperation(op) => write!(f, "unsupported operation; {}", op),
             FilterParseError(e) => write!(f, "error parsing filter; {}", e),
             FacetError(e) => write!(f, "error processing facet filter: {}", e),
         }
@@ -141,27 +160,17 @@ impl fmt::Display for Error {
 
 impl error::Error for Error {}
 
-#[derive(Debug)]
-pub enum UnsupportedOperation {
-    SchemaAlreadyExists,
-    CannotUpdateSchemaPrimaryKey,
-    CannotReorderSchemaAttribute,
-    CanOnlyIntroduceNewSchemaAttributesAtEnd,
-    CannotRemoveSchemaAttribute,
-}
+struct FilterParseError(PestError<Rule>);
 
-impl fmt::Display for UnsupportedOperation {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        use self::UnsupportedOperation::*;
-        match self {
-            SchemaAlreadyExists => write!(f, "Cannot update index which already have a schema"),
-            CannotUpdateSchemaPrimaryKey => write!(f, "Cannot update the primary key of a schema"),
-            CannotReorderSchemaAttribute => write!(f, "Cannot reorder the attributes of a schema"),
-            CanOnlyIntroduceNewSchemaAttributesAtEnd => {
-                write!(f, "Can only introduce new attributes at end of a schema")
-            }
-            CannotRemoveSchemaAttribute => write!(f, "Cannot remove attributes from a schema"),
-        }
+impl fmt::Display for FilterParseError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        use crate::pest_error::LineColLocation::*;
+
+        let (line, column) = match self.0.line_col {
+            Span((line, _), (column, _)) => (line, column),
+            Pos((line, column)) => (line, column),
+        };
+        write!(f, "parsing error on line {} at column {}: {}", line, column, self.0.variant.message())
     }
 }
 
diff --git a/meilisearch-core/src/facets.rs b/meilisearch-core/src/facets.rs
index dc8654915..cc1737eaf 100644
--- a/meilisearch-core/src/facets.rs
+++ b/meilisearch-core/src/facets.rs
@@ -13,7 +13,7 @@ use meilisearch_schema::{FieldId, Schema};
 use meilisearch_types::DocumentId;
 
 use crate::database::MainT;
-use crate::error::{FacetError, Error};
+use crate::error::{FacetError, MResult};
 use crate::store::BEU16;
 
 /// Data structure used to represent a boolean expression in the form of nested arrays.
@@ -34,14 +34,13 @@ impl FacetFilter {
         s: &str,
         schema: &Schema,
         attributes_for_faceting: &[FieldId],
-    ) -> Result<Self, FacetError> {
-
+    ) -> MResult<FacetFilter> {
         let parsed = serde_json::from_str::<Value>(s).map_err(|e| FacetError::ParsingError(e.to_string()))?;
         let mut filter = Vec::new();
         match parsed {
             Value::Array(and_exprs) => {
                 if and_exprs.is_empty() {
-                    return Err(FacetError::EmptyArray);
+                    return Err(FacetError::EmptyArray.into());
                 }
                 for expr in and_exprs {
                     match expr {
@@ -51,7 +50,7 @@ impl FacetFilter {
                         }
                         Value::Array(or_exprs) => {
                             if or_exprs.is_empty() {
-                                return Err(FacetError::EmptyArray);
+                                return Err(FacetError::EmptyArray.into());
                             }
                             let mut inner = Vec::new();
                             for expr in or_exprs {
@@ -60,17 +59,17 @@ impl FacetFilter {
                                         let key = FacetKey::from_str( &s, schema, attributes_for_faceting)?;
                                         inner.push(key);
                                     }
-                                    bad_value => return Err(FacetError::unexpected_token(&["String"], bad_value)),
+                                    bad_value => return Err(FacetError::unexpected_token(&["String"], bad_value).into()),
                                 }
                             }
                             filter.push(Either::Left(inner));
                         }
-                        bad_value => return Err(FacetError::unexpected_token(&["Array", "String"], bad_value)),
+                        bad_value => return Err(FacetError::unexpected_token(&["Array", "String"], bad_value).into()),
                     }
                 }
                 return Ok(Self(filter));
             }
-            bad_value => Err(FacetError::unexpected_token(&["Array"], bad_value)),
+            bad_value => Err(FacetError::unexpected_token(&["Array"], bad_value).into()),
         }
     }
 }
@@ -183,7 +182,7 @@ pub fn facet_map_from_docids(
     index: &crate::Index,
     document_ids: &[DocumentId],
     attributes_for_facetting: &[FieldId],
-) -> Result<HashMap<FacetKey, Vec<DocumentId>>, Error> {
+) -> MResult<HashMap<FacetKey, Vec<DocumentId>>> {
     let mut facet_map = HashMap::new();
     for document_id in document_ids {
         for result in index
@@ -210,7 +209,7 @@ pub fn facet_map_from_docs(
     schema: &Schema,
     documents: &HashMap<DocumentId, IndexMap<String, Value>>,
     attributes_for_facetting: &[FieldId],
-) -> Result<HashMap<FacetKey, Vec<DocumentId>>, Error> {
+) -> MResult<HashMap<FacetKey, Vec<DocumentId>>> {
     let mut facet_map = HashMap::new();
     let attributes_for_facetting = attributes_for_facetting
         .iter()
diff --git a/meilisearch-core/src/lib.rs b/meilisearch-core/src/lib.rs
index a9938bb73..e468a794e 100644
--- a/meilisearch-core/src/lib.rs
+++ b/meilisearch-core/src/lib.rs
@@ -26,7 +26,7 @@ pub mod settings;
 pub mod store;
 pub mod update;
 
-pub use self::database::{BoxUpdateFn, Database, DatabaseOptions, MainT, UpdateT};
+pub use self::database::{BoxUpdateFn, Database, DatabaseOptions, MainT, UpdateT, MainWriter, MainReader, UpdateWriter, UpdateReader};
 pub use self::error::{Error, HeedError, FstError, MResult, pest_error, FacetError};
 pub use self::filters::Filter;
 pub use self::number::{Number, ParseNumberError};
diff --git a/meilisearch-core/src/query_builder.rs b/meilisearch-core/src/query_builder.rs
index c9ed1933e..72accfcde 100644
--- a/meilisearch-core/src/query_builder.rs
+++ b/meilisearch-core/src/query_builder.rs
@@ -268,7 +268,7 @@ mod tests {
             let alternatives = self
                 .index
                 .synonyms
-                .synonyms(&writer, word.as_bytes())
+                .synonyms_fst(&writer, word.as_bytes())
                 .unwrap();
 
             let new = sdset_into_fstset(&new);
diff --git a/meilisearch-core/src/query_tree.rs b/meilisearch-core/src/query_tree.rs
index 2687028a0..4a3a622b2 100644
--- a/meilisearch-core/src/query_tree.rs
+++ b/meilisearch-core/src/query_tree.rs
@@ -147,7 +147,7 @@ fn split_best_frequency<'a>(reader: &heed::RoTxn<MainT>, ctx: &Context, word: &'
 
 fn fetch_synonyms(reader: &heed::RoTxn<MainT>, ctx: &Context, words: &[&str]) -> MResult<Vec<Vec<String>>> {
     let words = normalize_str(&words.join(" "));
-    let set = ctx.synonyms.synonyms(reader, words.as_bytes())?;
+    let set = ctx.synonyms.synonyms_fst(reader, words.as_bytes())?;
 
     let mut strings = Vec::new();
     let mut stream = set.stream();
diff --git a/meilisearch-core/src/store/documents_fields_counts.rs b/meilisearch-core/src/store/documents_fields_counts.rs
index 69bacd5f7..f0d23c99b 100644
--- a/meilisearch-core/src/store/documents_fields_counts.rs
+++ b/meilisearch-core/src/store/documents_fields_counts.rs
@@ -4,6 +4,7 @@ use crate::DocumentId;
 use heed::types::OwnedType;
 use heed::Result as ZResult;
 use meilisearch_schema::IndexedPos;
+use crate::MResult;
 
 #[derive(Copy, Clone)]
 pub struct DocumentsFieldsCounts {
@@ -60,7 +61,7 @@ impl DocumentsFieldsCounts {
         Ok(DocumentFieldsCountsIter { iter })
     }
 
-    pub fn documents_ids<'txn>(self, reader: &'txn heed::RoTxn<MainT>) -> ZResult<DocumentsIdsIter<'txn>> {
+    pub fn documents_ids<'txn>(self, reader: &'txn heed::RoTxn<MainT>) -> MResult<DocumentsIdsIter<'txn>> {
         let iter = self.documents_fields_counts.iter(reader)?;
         Ok(DocumentsIdsIter {
             last_seen_id: None,
@@ -102,7 +103,7 @@ pub struct DocumentsIdsIter<'txn> {
 }
 
 impl Iterator for DocumentsIdsIter<'_> {
-    type Item = ZResult<DocumentId>;
+    type Item = MResult<DocumentId>;
 
     fn next(&mut self) -> Option<Self::Item> {
         for result in &mut self.iter {
@@ -114,7 +115,7 @@ impl Iterator for DocumentsIdsIter<'_> {
                         return Some(Ok(document_id));
                     }
                 }
-                Err(e) => return Some(Err(e)),
+                Err(e) => return Some(Err(e.into())),
             }
         }
         None
diff --git a/meilisearch-core/src/store/main.rs b/meilisearch-core/src/store/main.rs
index 864970320..f1ef6fc5e 100644
--- a/meilisearch-core/src/store/main.rs
+++ b/meilisearch-core/src/store/main.rs
@@ -2,14 +2,13 @@ use std::borrow::Cow;
 use std::collections::HashMap;
 
 use chrono::{DateTime, Utc};
-use heed::Result as ZResult;
 use heed::types::{ByteSlice, OwnedType, SerdeBincode, Str};
 use meilisearch_schema::{FieldId, Schema};
 use meilisearch_types::DocumentId;
 use sdset::Set;
 
 use crate::database::MainT;
-use crate::RankedMap;
+use crate::{RankedMap, MResult};
 use crate::settings::RankingRule;
 use crate::{FstSetCow, FstMapCow};
 use super::{CowSet, DocumentsIds};
@@ -41,75 +40,73 @@ pub struct Main {
 }
 
 impl Main {
-    pub fn clear(self, writer: &mut heed::RwTxn<MainT>) -> ZResult<()> {
-        self.main.clear(writer)
+    pub fn clear(self, writer: &mut heed::RwTxn<MainT>) -> MResult<()> {
+        Ok(self.main.clear(writer)?)
     }
 
-    pub fn put_name(self, writer: &mut heed::RwTxn<MainT>, name: &str) -> ZResult<()> {
-        self.main.put::<_, Str, Str>(writer, NAME_KEY, name)
+    pub fn put_name(self, writer: &mut heed::RwTxn<MainT>, name: &str) -> MResult<()> {
+        Ok(self.main.put::<_, Str, Str>(writer, NAME_KEY, name)?)
     }
 
-    pub fn name(self, reader: &heed::RoTxn<MainT>) -> ZResult<Option<String>> {
+    pub fn name(self, reader: &heed::RoTxn<MainT>) -> MResult<Option<String>> {
         Ok(self
             .main
             .get::<_, Str, Str>(reader, NAME_KEY)?
             .map(|name| name.to_owned()))
     }
 
-    pub fn put_created_at(self, writer: &mut heed::RwTxn<MainT>) -> ZResult<()> {
-        self.main
-            .put::<_, Str, SerdeDatetime>(writer, CREATED_AT_KEY, &Utc::now())
+    pub fn put_created_at(self, writer: &mut heed::RwTxn<MainT>) -> MResult<()> {
+        Ok(self.main.put::<_, Str, SerdeDatetime>(writer, CREATED_AT_KEY, &Utc::now())?)
     }
 
-    pub fn created_at(self, reader: &heed::RoTxn<MainT>) -> ZResult<Option<DateTime<Utc>>> {
-        self.main.get::<_, Str, SerdeDatetime>(reader, CREATED_AT_KEY)
+    pub fn created_at(self, reader: &heed::RoTxn<MainT>) -> MResult<Option<DateTime<Utc>>> {
+        Ok(self.main.get::<_, Str, SerdeDatetime>(reader, CREATED_AT_KEY)?)
     }
 
-    pub fn put_updated_at(self, writer: &mut heed::RwTxn<MainT>) -> ZResult<()> {
-        self.main
-            .put::<_, Str, SerdeDatetime>(writer, UPDATED_AT_KEY, &Utc::now())
+    pub fn put_updated_at(self, writer: &mut heed::RwTxn<MainT>) -> MResult<()> {
+        Ok(self.main.put::<_, Str, SerdeDatetime>(writer, UPDATED_AT_KEY, &Utc::now())?)
     }
 
-    pub fn updated_at(self, reader: &heed::RoTxn<MainT>) -> ZResult<Option<DateTime<Utc>>> {
-        self.main.get::<_, Str, SerdeDatetime>(reader, UPDATED_AT_KEY)
+    pub fn updated_at(self, reader: &heed::RoTxn<MainT>) -> MResult<Option<DateTime<Utc>>> {
+        Ok(self.main.get::<_, Str, SerdeDatetime>(reader, UPDATED_AT_KEY)?)
     }
 
-    pub fn put_internal_docids(self, writer: &mut heed::RwTxn<MainT>, ids: &sdset::Set<DocumentId>) -> ZResult<()> {
-        self.main.put::<_, Str, DocumentsIds>(writer, INTERNAL_DOCIDS_KEY, ids)
+    pub fn put_internal_docids(self, writer: &mut heed::RwTxn<MainT>, ids: &sdset::Set<DocumentId>) -> MResult<()> {
+        Ok(self.main.put::<_, Str, DocumentsIds>(writer, INTERNAL_DOCIDS_KEY, ids)?)
     }
 
-    pub fn internal_docids<'txn>(self, reader: &'txn heed::RoTxn<MainT>) -> ZResult<Cow<'txn, sdset::Set<DocumentId>>> {
+    pub fn internal_docids<'txn>(self, reader: &'txn heed::RoTxn<MainT>) -> MResult<Cow<'txn, sdset::Set<DocumentId>>> {
         match self.main.get::<_, Str, DocumentsIds>(reader, INTERNAL_DOCIDS_KEY)? {
             Some(ids) => Ok(ids),
             None => Ok(Cow::default()),
         }
     }
 
-    pub fn merge_internal_docids(self, writer: &mut heed::RwTxn<MainT>, new_ids: &sdset::Set<DocumentId>) -> ZResult<()> {
+    pub fn merge_internal_docids(self, writer: &mut heed::RwTxn<MainT>, new_ids: &sdset::Set<DocumentId>) -> MResult<()> {
         use sdset::SetOperation;
 
         // We do an union of the old and new internal ids.
         let internal_docids = self.internal_docids(writer)?;
         let internal_docids = sdset::duo::Union::new(&internal_docids, new_ids).into_set_buf();
-        self.put_internal_docids(writer, &internal_docids)
+        Ok(self.put_internal_docids(writer, &internal_docids)?)
     }
 
-    pub fn remove_internal_docids(self, writer: &mut heed::RwTxn<MainT>, ids: &sdset::Set<DocumentId>) -> ZResult<()> {
+    pub fn remove_internal_docids(self, writer: &mut heed::RwTxn<MainT>, ids: &sdset::Set<DocumentId>) -> MResult<()> {
         use sdset::SetOperation;
 
         // We do a difference of the old and new internal ids.
         let internal_docids = self.internal_docids(writer)?;
         let internal_docids = sdset::duo::Difference::new(&internal_docids, ids).into_set_buf();
-        self.put_internal_docids(writer, &internal_docids)
+        Ok(self.put_internal_docids(writer, &internal_docids)?)
     }
 
-    pub fn put_external_docids<A>(self, writer: &mut heed::RwTxn<MainT>, ids: &fst::Map<A>) -> ZResult<()>
+    pub fn put_external_docids<A>(self, writer: &mut heed::RwTxn<MainT>, ids: &fst::Map<A>) -> MResult<()>
     where A: AsRef<[u8]>,
     {
-        self.main.put::<_, Str, ByteSlice>(writer, EXTERNAL_DOCIDS_KEY, ids.as_fst().as_bytes())
+        Ok(self.main.put::<_, Str, ByteSlice>(writer, EXTERNAL_DOCIDS_KEY, ids.as_fst().as_bytes())?)
     }
 
-    pub fn merge_external_docids<A>(self, writer: &mut heed::RwTxn<MainT>, new_docids: &fst::Map<A>) -> ZResult<()>
+    pub fn merge_external_docids<A>(self, writer: &mut heed::RwTxn<MainT>, new_docids: &fst::Map<A>) -> MResult<()>
     where A: AsRef<[u8]>,
     {
         use fst::{Streamer, IntoStreamer};
@@ -124,10 +121,10 @@ impl Main {
         drop(op);
 
         let external_docids = build.into_map();
-        self.put_external_docids(writer, &external_docids)
+        Ok(self.put_external_docids(writer, &external_docids)?)
     }
 
-    pub fn remove_external_docids<A>(self, writer: &mut heed::RwTxn<MainT>, ids: &fst::Map<A>) -> ZResult<()>
+    pub fn remove_external_docids<A>(self, writer: &mut heed::RwTxn<MainT>, ids: &fst::Map<A>) -> MResult<()>
     where A: AsRef<[u8]>,
     {
         use fst::{Streamer, IntoStreamer};
@@ -145,74 +142,90 @@ impl Main {
         self.put_external_docids(writer, &external_docids)
     }
 
-    pub fn external_docids(self, reader: &heed::RoTxn<MainT>) -> ZResult<FstMapCow> {
+    pub fn external_docids(self, reader: &heed::RoTxn<MainT>) -> MResult<FstMapCow> {
         match self.main.get::<_, Str, ByteSlice>(reader, EXTERNAL_DOCIDS_KEY)? {
             Some(bytes) => Ok(fst::Map::new(bytes).unwrap().map_data(Cow::Borrowed).unwrap()),
             None => Ok(fst::Map::default().map_data(Cow::Owned).unwrap()),
         }
     }
 
-    pub fn external_to_internal_docid(self, reader: &heed::RoTxn<MainT>, external_docid: &str) -> ZResult<Option<DocumentId>> {
+    pub fn external_to_internal_docid(self, reader: &heed::RoTxn<MainT>, external_docid: &str) -> MResult<Option<DocumentId>> {
         let external_ids = self.external_docids(reader)?;
         Ok(external_ids.get(external_docid).map(|id| DocumentId(id as u32)))
     }
 
-    pub fn put_words_fst<A: AsRef<[u8]>>(self, writer: &mut heed::RwTxn<MainT>, fst: &fst::Set<A>) -> ZResult<()> {
-        self.main.put::<_, Str, ByteSlice>(writer, WORDS_KEY, fst.as_fst().as_bytes())
-    }
-
-    pub fn words_fst(self, reader: &heed::RoTxn<MainT>) -> ZResult<FstSetCow> {
+    pub fn words_fst(self, reader: &heed::RoTxn<MainT>) -> MResult<FstSetCow> {
         match self.main.get::<_, Str, ByteSlice>(reader, WORDS_KEY)? {
             Some(bytes) => Ok(fst::Set::new(bytes).unwrap().map_data(Cow::Borrowed).unwrap()),
             None => Ok(fst::Set::default().map_data(Cow::Owned).unwrap()),
         }
     }
 
-    pub fn put_schema(self, writer: &mut heed::RwTxn<MainT>, schema: &Schema) -> ZResult<()> {
-        self.main.put::<_, Str, SerdeBincode<Schema>>(writer, SCHEMA_KEY, schema)
+    pub fn put_words_fst<A: AsRef<[u8]>>(self, writer: &mut heed::RwTxn<MainT>, fst: &fst::Set<A>) -> MResult<()> {
+        Ok(self.main.put::<_, Str, ByteSlice>(writer, WORDS_KEY, fst.as_fst().as_bytes())?)
     }
 
-    pub fn schema(self, reader: &heed::RoTxn<MainT>) -> ZResult<Option<Schema>> {
-        self.main.get::<_, Str, SerdeBincode<Schema>>(reader, SCHEMA_KEY)
+    pub fn put_schema(self, writer: &mut heed::RwTxn<MainT>, schema: &Schema) -> MResult<()> {
+        Ok(self.main.put::<_, Str, SerdeBincode<Schema>>(writer, SCHEMA_KEY, schema)?)
     }
 
-    pub fn delete_schema(self, writer: &mut heed::RwTxn<MainT>) -> ZResult<bool> {
-        self.main.delete::<_, Str>(writer, SCHEMA_KEY)
+    pub fn schema(self, reader: &heed::RoTxn<MainT>) -> MResult<Option<Schema>> {
+        Ok(self.main.get::<_, Str, SerdeBincode<Schema>>(reader, SCHEMA_KEY)?)
     }
 
-    pub fn put_ranked_map(self, writer: &mut heed::RwTxn<MainT>, ranked_map: &RankedMap) -> ZResult<()> {
-        self.main.put::<_, Str, SerdeBincode<RankedMap>>(writer, RANKED_MAP_KEY, &ranked_map)
+    pub fn delete_schema(self, writer: &mut heed::RwTxn<MainT>) -> MResult<bool> {
+        Ok(self.main.delete::<_, Str>(writer, SCHEMA_KEY)?)
     }
 
-    pub fn ranked_map(self, reader: &heed::RoTxn<MainT>) -> ZResult<Option<RankedMap>> {
-        self.main.get::<_, Str, SerdeBincode<RankedMap>>(reader, RANKED_MAP_KEY)
+    pub fn put_ranked_map(self, writer: &mut heed::RwTxn<MainT>, ranked_map: &RankedMap) -> MResult<()> {
+        Ok(self.main.put::<_, Str, SerdeBincode<RankedMap>>(writer, RANKED_MAP_KEY, &ranked_map)?)
     }
 
-    pub fn put_synonyms_fst<A: AsRef<[u8]>>(self, writer: &mut heed::RwTxn<MainT>, fst: &fst::Set<A>) -> ZResult<()> {
+    pub fn ranked_map(self, reader: &heed::RoTxn<MainT>) -> MResult<Option<RankedMap>> {
+        Ok(self.main.get::<_, Str, SerdeBincode<RankedMap>>(reader, RANKED_MAP_KEY)?)
+    }
+
+    pub fn put_synonyms_fst<A: AsRef<[u8]>>(self, writer: &mut heed::RwTxn<MainT>, fst: &fst::Set<A>) -> MResult<()> {
         let bytes = fst.as_fst().as_bytes();
-        self.main.put::<_, Str, ByteSlice>(writer, SYNONYMS_KEY, bytes)
+        Ok(self.main.put::<_, Str, ByteSlice>(writer, SYNONYMS_KEY, bytes)?)
     }
 
-    pub fn synonyms_fst(self, reader: &heed::RoTxn<MainT>) -> ZResult<FstSetCow> {
+    pub(crate) fn synonyms_fst(self, reader: &heed::RoTxn<MainT>) -> MResult<FstSetCow> {
         match self.main.get::<_, Str, ByteSlice>(reader, SYNONYMS_KEY)? {
             Some(bytes) => Ok(fst::Set::new(bytes).unwrap().map_data(Cow::Borrowed).unwrap()),
             None => Ok(fst::Set::default().map_data(Cow::Owned).unwrap()),
         }
     }
 
-    pub fn put_stop_words_fst<A: AsRef<[u8]>>(self, writer: &mut heed::RwTxn<MainT>, fst: &fst::Set<A>) -> ZResult<()> {
-        let bytes = fst.as_fst().as_bytes();
-        self.main.put::<_, Str, ByteSlice>(writer, STOP_WORDS_KEY, bytes)
+    pub fn synonyms(self, reader: &heed::RoTxn<MainT>) -> MResult<Vec<String>> {
+        let synonyms = self
+            .synonyms_fst(&reader)?
+            .stream()
+            .into_strs()?;
+        Ok(synonyms)
     }
 
-    pub fn stop_words_fst(self, reader: &heed::RoTxn<MainT>) -> ZResult<FstSetCow> {
+    pub fn put_stop_words_fst<A: AsRef<[u8]>>(self, writer: &mut heed::RwTxn<MainT>, fst: &fst::Set<A>) -> MResult<()> {
+        let bytes = fst.as_fst().as_bytes();
+        Ok(self.main.put::<_, Str, ByteSlice>(writer, STOP_WORDS_KEY, bytes)?)
+    }
+
+    pub(crate) fn stop_words_fst(self, reader: &heed::RoTxn<MainT>) -> MResult<FstSetCow> {
         match self.main.get::<_, Str, ByteSlice>(reader, STOP_WORDS_KEY)? {
             Some(bytes) => Ok(fst::Set::new(bytes).unwrap().map_data(Cow::Borrowed).unwrap()),
             None => Ok(fst::Set::default().map_data(Cow::Owned).unwrap()),
         }
     }
 
-    pub fn put_number_of_documents<F>(self, writer: &mut heed::RwTxn<MainT>, f: F) -> ZResult<u64>
+    pub fn stop_words(self, reader: &heed::RoTxn<MainT>) -> MResult<Vec<String>> {
+        let stop_word_list = self
+            .stop_words_fst(reader)?
+            .stream()
+            .into_strs()?;
+        Ok(stop_word_list)
+    }
+
+    pub fn put_number_of_documents<F>(self, writer: &mut heed::RwTxn<MainT>, f: F) -> MResult<u64>
     where
         F: Fn(u64) -> u64,
     {
@@ -222,11 +235,10 @@ impl Main {
         Ok(new)
     }
 
-    pub fn number_of_documents(self, reader: &heed::RoTxn<MainT>) -> ZResult<u64> {
+    pub fn number_of_documents(self, reader: &heed::RoTxn<MainT>) -> MResult<u64> {
         match self
             .main
-            .get::<_, Str, OwnedType<u64>>(reader, NUMBER_OF_DOCUMENTS_KEY)?
-        {
+            .get::<_, Str, OwnedType<u64>>(reader, NUMBER_OF_DOCUMENTS_KEY)? {
             Some(value) => Ok(value),
             None => Ok(0),
         }
@@ -235,13 +247,12 @@ impl Main {
     pub fn put_fields_distribution(
         self,
         writer: &mut heed::RwTxn<MainT>,
-        fields_distribution: &FreqsMap,
-    ) -> ZResult<()> {
-        self.main
-            .put::<_, Str, SerdeFreqsMap>(writer, FIELDS_DISTRIBUTION_KEY, fields_distribution)
+        fields_frequency: &FreqsMap,
+    ) -> MResult<()> {
+        Ok(self.main.put::<_, Str, SerdeFreqsMap>(writer, FIELDS_DISTRIBUTION_KEY, fields_frequency)?)
     }
 
-    pub fn fields_distribution(&self, reader: &heed::RoTxn<MainT>) -> ZResult<Option<FreqsMap>> {
+    pub fn fields_distribution(&self, reader: &heed::RoTxn<MainT>) -> MResult<Option<FreqsMap>> {
         match self
             .main
             .get::<_, Str, SerdeFreqsMap>(reader, FIELDS_DISTRIBUTION_KEY)?
@@ -251,51 +262,50 @@ impl Main {
         }
     }
 
-    pub fn attributes_for_faceting<'txn>(&self, reader: &'txn heed::RoTxn<MainT>) -> ZResult<Option<Cow<'txn, Set<FieldId>>>> {
-        self.main.get::<_, Str, CowSet<FieldId>>(reader, ATTRIBUTES_FOR_FACETING_KEY)
+    pub fn attributes_for_faceting<'txn>(&self, reader: &'txn heed::RoTxn<MainT>) -> MResult<Option<Cow<'txn, Set<FieldId>>>> {
+        Ok(self.main.get::<_, Str, CowSet<FieldId>>(reader, ATTRIBUTES_FOR_FACETING_KEY)?)
     }
 
-    pub fn put_attributes_for_faceting(self, writer: &mut heed::RwTxn<MainT>, attributes: &Set<FieldId>) -> ZResult<()> {
-        self.main.put::<_, Str, CowSet<FieldId>>(writer, ATTRIBUTES_FOR_FACETING_KEY, attributes)
+    pub fn put_attributes_for_faceting(self, writer: &mut heed::RwTxn<MainT>, attributes: &Set<FieldId>) -> MResult<()> {
+        Ok(self.main.put::<_, Str, CowSet<FieldId>>(writer, ATTRIBUTES_FOR_FACETING_KEY, attributes)?)
     }
 
-    pub fn delete_attributes_for_faceting(self, writer: &mut heed::RwTxn<MainT>) -> ZResult<bool> {
-        self.main.delete::<_, Str>(writer, ATTRIBUTES_FOR_FACETING_KEY)
+    pub fn delete_attributes_for_faceting(self, writer: &mut heed::RwTxn<MainT>) -> MResult<bool> {
+        Ok(self.main.delete::<_, Str>(writer, ATTRIBUTES_FOR_FACETING_KEY)?)
     }
 
-    pub fn ranking_rules(&self, reader: &heed::RoTxn<MainT>) -> ZResult<Option<Vec<RankingRule>>> {
-        self.main.get::<_, Str, SerdeBincode<Vec<RankingRule>>>(reader, RANKING_RULES_KEY)
+    pub fn ranking_rules(&self, reader: &heed::RoTxn<MainT>) -> MResult<Option<Vec<RankingRule>>> {
+        Ok(self.main.get::<_, Str, SerdeBincode<Vec<RankingRule>>>(reader, RANKING_RULES_KEY)?)
     }
 
-    pub fn put_ranking_rules(self, writer: &mut heed::RwTxn<MainT>, value: &[RankingRule]) -> ZResult<()> {
-        self.main.put::<_, Str, SerdeBincode<Vec<RankingRule>>>(writer, RANKING_RULES_KEY, &value.to_vec())
+    pub fn put_ranking_rules(self, writer: &mut heed::RwTxn<MainT>, value: &[RankingRule]) -> MResult<()> {
+        Ok(self.main.put::<_, Str, SerdeBincode<Vec<RankingRule>>>(writer, RANKING_RULES_KEY, &value.to_vec())?)
     }
 
-    pub fn delete_ranking_rules(self, writer: &mut heed::RwTxn<MainT>) -> ZResult<bool> {
-        self.main.delete::<_, Str>(writer, RANKING_RULES_KEY)
+    pub fn delete_ranking_rules(self, writer: &mut heed::RwTxn<MainT>) -> MResult<bool> {
+        Ok(self.main.delete::<_, Str>(writer, RANKING_RULES_KEY)?)
     }
 
-    pub fn distinct_attribute(&self, reader: &heed::RoTxn<MainT>) -> ZResult<Option<String>> {
+    pub fn distinct_attribute(&self, reader: &heed::RoTxn<MainT>) -> MResult<Option<String>> {
         if let Some(value) = self.main.get::<_, Str, Str>(reader, DISTINCT_ATTRIBUTE_KEY)? {
             return Ok(Some(value.to_owned()))
         }
         return Ok(None)
     }
 
-    pub fn put_distinct_attribute(self, writer: &mut heed::RwTxn<MainT>, value: &str) -> ZResult<()> {
-        self.main.put::<_, Str, Str>(writer, DISTINCT_ATTRIBUTE_KEY, value)
+    pub fn put_distinct_attribute(self, writer: &mut heed::RwTxn<MainT>, value: &str) -> MResult<()> {
+        Ok(self.main.put::<_, Str, Str>(writer, DISTINCT_ATTRIBUTE_KEY, value)?)
     }
 
-    pub fn delete_distinct_attribute(self, writer: &mut heed::RwTxn<MainT>) -> ZResult<bool> {
-        self.main.delete::<_, Str>(writer, DISTINCT_ATTRIBUTE_KEY)
+    pub fn delete_distinct_attribute(self, writer: &mut heed::RwTxn<MainT>) -> MResult<bool> {
+        Ok(self.main.delete::<_, Str>(writer, DISTINCT_ATTRIBUTE_KEY)?)
     }
 
-    pub fn put_customs(self, writer: &mut heed::RwTxn<MainT>, customs: &[u8]) -> ZResult<()> {
-        self.main
-            .put::<_, Str, ByteSlice>(writer, CUSTOMS_KEY, customs)
+    pub fn put_customs(self, writer: &mut heed::RwTxn<MainT>, customs: &[u8]) -> MResult<()> {
+        Ok(self.main.put::<_, Str, ByteSlice>(writer, CUSTOMS_KEY, customs)?)
     }
 
-    pub fn customs<'txn>(self, reader: &'txn heed::RoTxn<MainT>) -> ZResult<Option<&'txn [u8]>> {
-        self.main.get::<_, Str, ByteSlice>(reader, CUSTOMS_KEY)
+    pub fn customs<'txn>(self, reader: &'txn heed::RoTxn<MainT>) -> MResult<Option<&'txn [u8]>> {
+        Ok(self.main.get::<_, Str, ByteSlice>(reader, CUSTOMS_KEY)?)
     }
 }
diff --git a/meilisearch-core/src/store/mod.rs b/meilisearch-core/src/store/mod.rs
index d19d3f7d3..fa5baa831 100644
--- a/meilisearch-core/src/store/mod.rs
+++ b/meilisearch-core/src/store/mod.rs
@@ -31,7 +31,6 @@ use std::collections::HashSet;
 use std::convert::TryInto;
 use std::{mem, ptr};
 
-use heed::Result as ZResult;
 use heed::{BytesEncode, BytesDecode};
 use meilisearch_schema::{IndexedPos, FieldId};
 use sdset::{Set, SetBuf};
@@ -279,14 +278,14 @@ impl Index {
         }
     }
 
-    pub fn customs_update(&self, writer: &mut heed::RwTxn<UpdateT>, customs: Vec<u8>) -> ZResult<u64> {
+    pub fn customs_update(&self, writer: &mut heed::RwTxn<UpdateT>, customs: Vec<u8>) -> MResult<u64> {
         let _ = self.updates_notifier.send(UpdateEvent::NewUpdate);
-        update::push_customs_update(writer, self.updates, self.updates_results, customs)
+        Ok(update::push_customs_update(writer, self.updates, self.updates_results, customs)?)
     }
 
-    pub fn settings_update(&self, writer: &mut heed::RwTxn<UpdateT>, update: SettingsUpdate) -> ZResult<u64> {
+    pub fn settings_update(&self, writer: &mut heed::RwTxn<UpdateT>, update: SettingsUpdate) -> MResult<u64> {
         let _ = self.updates_notifier.send(UpdateEvent::NewUpdate);
-        update::push_settings_update(writer, self.updates, self.updates_results, update)
+        Ok(update::push_settings_update(writer, self.updates, self.updates_results, update)?)
     }
 
     pub fn documents_addition<D>(&self) -> update::DocumentsAddition<D> {
diff --git a/meilisearch-core/src/store/synonyms.rs b/meilisearch-core/src/store/synonyms.rs
index 1ec8d313c..bf7472f96 100644
--- a/meilisearch-core/src/store/synonyms.rs
+++ b/meilisearch-core/src/store/synonyms.rs
@@ -4,7 +4,7 @@ use heed::Result as ZResult;
 use heed::types::ByteSlice;
 
 use crate::database::MainT;
-use crate::FstSetCow;
+use crate::{FstSetCow, MResult};
 
 #[derive(Copy, Clone)]
 pub struct Synonyms {
@@ -27,10 +27,18 @@ impl Synonyms {
         self.synonyms.clear(writer)
     }
 
-    pub fn synonyms<'txn>(self, reader: &'txn heed::RoTxn<MainT>, word: &[u8]) -> ZResult<FstSetCow<'txn>> {
+    pub(crate) fn synonyms_fst<'txn>(self, reader: &'txn heed::RoTxn<MainT>, word: &[u8]) -> ZResult<FstSetCow<'txn>> {
         match self.synonyms.get(reader, word)? {
             Some(bytes) => Ok(fst::Set::new(bytes).unwrap().map_data(Cow::Borrowed).unwrap()),
             None => Ok(fst::Set::default().map_data(Cow::Owned).unwrap()),
         }
     }
+
+    pub fn synonyms(self, reader: &heed::RoTxn<MainT>, word: &[u8]) -> MResult<Vec<String>> {
+        let synonyms = self
+            .synonyms_fst(&reader, word)?
+            .stream()
+            .into_strs()?;
+        Ok(synonyms)
+    }
 }
diff --git a/meilisearch-core/src/update/customs_update.rs b/meilisearch-core/src/update/customs_update.rs
index a413d13a6..a3a66e61d 100644
--- a/meilisearch-core/src/update/customs_update.rs
+++ b/meilisearch-core/src/update/customs_update.rs
@@ -1,14 +1,13 @@
-use heed::Result as ZResult;
 
 use crate::database::{MainT, UpdateT};
-use crate::store;
+use crate::{store, MResult};
 use crate::update::{next_update_id, Update};
 
 pub fn apply_customs_update(
     writer: &mut heed::RwTxn<MainT>,
     main_store: store::Main,
     customs: &[u8],
-) -> ZResult<()> {
+) -> MResult<()> {
     main_store.put_customs(writer, customs)
 }
 
@@ -17,7 +16,7 @@ pub fn push_customs_update(
     updates_store: store::Updates,
     updates_results_store: store::UpdatesResults,
     customs: Vec<u8>,
-) -> ZResult<u64> {
+) -> MResult<u64> {
     let last_update_id = next_update_id(writer, updates_store, updates_results_store)?;
 
     let update = Update::customs(customs);
diff --git a/meilisearch-error/Cargo.toml b/meilisearch-error/Cargo.toml
new file mode 100644
index 000000000..ad77978b1
--- /dev/null
+++ b/meilisearch-error/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "meilisearch-error"
+version = "0.10.1"
+authors = ["marin <postma.marin@protonmail.com>"]
+edition = "2018"
+
+[dependencies]
+actix-http = "1.0.1"
diff --git a/meilisearch-error/src/lib.rs b/meilisearch-error/src/lib.rs
new file mode 100644
index 000000000..1c8fc4e78
--- /dev/null
+++ b/meilisearch-error/src/lib.rs
@@ -0,0 +1,174 @@
+use std::fmt;
+
+use actix_http::http::StatusCode;
+
+pub trait ErrorCode: std::error::Error {
+    fn error_code(&self) -> Code;
+
+    /// returns the HTTP status code ascociated with the error
+    fn http_status(&self) -> StatusCode {
+        self.error_code().http()
+    }
+
+    /// returns the doc url ascociated with the error
+    fn error_url(&self) -> String {
+        self.error_code().url()
+    }
+
+    /// returns error name, used as error code
+    fn error_name(&self) -> String {
+        self.error_code().name()
+    }
+
+    /// return the error type
+    fn error_type(&self) -> String {
+        self.error_code().type_()
+    }
+}
+
+enum ErrorType {
+    InternalError,
+    InvalidRequest,
+    Authentication,
+}
+
+impl fmt::Display for ErrorType {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        use ErrorType::*;
+
+        match self {
+            InternalError => write!(f, "internal_error"),
+            InvalidRequest => write!(f, "invalid_request"),
+            Authentication => write!(f, "authentication"),
+        }
+    }
+}
+
+pub enum Code {
+    // index related error
+    CreateIndex,
+    IndexAlreadyExists,
+    IndexNotFound,
+    InvalidIndexUid,
+    OpenIndex,
+
+    // invalid state error
+    InvalidState,
+    MissingPrimaryKey,
+    PrimaryKeyAlreadyPresent,
+
+    MaxFieldsLimitExceeded,
+    MissingDocumentId,
+
+    Facet,
+    Filter,
+
+    BadParameter,
+    BadRequest,
+    DocumentNotFound,
+    Internal,
+    InvalidToken,
+    Maintenance,
+    MissingAuthorizationHeader,
+    MissingHeader,
+    NotFound,
+    PayloadTooLarge,
+    RetrieveDocument,
+    SearchDocuments,
+    UnsupportedMediaType,
+}
+
+impl Code {
+
+    /// ascociate a `Code` variant to the actual ErrCode
+    fn err_code(&self) -> ErrCode {
+        use Code::*;
+
+        match self {
+            // index related errors
+            CreateIndex => ErrCode::invalid("create_index", StatusCode::BAD_REQUEST),
+            IndexAlreadyExists => ErrCode::invalid("existing_index", StatusCode::BAD_REQUEST),
+            IndexNotFound => ErrCode::invalid("index_not_found", StatusCode::NOT_FOUND), InvalidIndexUid => ErrCode::invalid("invalid_index_uid", StatusCode::BAD_REQUEST),
+            OpenIndex => ErrCode::internal("open_index", StatusCode::INTERNAL_SERVER_ERROR),
+
+            // invalid state error
+            InvalidState => ErrCode::internal("invalid_state", StatusCode::INTERNAL_SERVER_ERROR),
+            MissingPrimaryKey => ErrCode::internal("missing_primary_key", StatusCode::INTERNAL_SERVER_ERROR),
+            PrimaryKeyAlreadyPresent => ErrCode::internal("primary_key_already_present", StatusCode::INTERNAL_SERVER_ERROR),
+
+            // invalid document
+            MaxFieldsLimitExceeded => ErrCode::invalid("max_field_limit_exceeded", StatusCode::BAD_REQUEST),
+            MissingDocumentId => ErrCode::invalid("missing_document_id", StatusCode::BAD_REQUEST),
+
+            Facet => ErrCode::invalid("invalid_facet", StatusCode::BAD_REQUEST),
+            Filter => ErrCode::invalid("invalid_filter", StatusCode::BAD_REQUEST),
+
+            BadParameter => ErrCode::invalid("bad_parameter", StatusCode::BAD_REQUEST),
+            BadRequest => ErrCode::invalid("bad_request", StatusCode::BAD_REQUEST),
+            DocumentNotFound => ErrCode::internal("document_not_found", StatusCode::NOT_FOUND),
+            Internal => ErrCode::internal("internal", StatusCode::INTERNAL_SERVER_ERROR),
+            InvalidToken => ErrCode::authentication("invalid_token", StatusCode::UNAUTHORIZED),
+            Maintenance =>  ErrCode::internal("maintenance", StatusCode::SERVICE_UNAVAILABLE),
+            MissingAuthorizationHeader => ErrCode::authentication("missing_authorization_header", StatusCode::FORBIDDEN),
+            MissingHeader => ErrCode::authentication("missing_header", StatusCode::UNAUTHORIZED),
+            NotFound => ErrCode::invalid("not_found", StatusCode::NOT_FOUND),
+            PayloadTooLarge => ErrCode::invalid("payload_too_large", StatusCode::PAYLOAD_TOO_LARGE),
+            RetrieveDocument => ErrCode::internal("retrieve_document", StatusCode::BAD_REQUEST),
+            SearchDocuments => ErrCode::internal("search_error", StatusCode::BAD_REQUEST),
+            UnsupportedMediaType => ErrCode::invalid("unsupported_media_type", StatusCode::UNSUPPORTED_MEDIA_TYPE),
+        }
+    }
+
+    /// return the HTTP status code ascociated with the `Code`
+    fn http(&self) -> StatusCode {
+        self.err_code().status_code
+    }
+
+    /// return error name, used as error code
+    fn name(&self) -> String {
+        self.err_code().error_name.to_string()
+    }
+
+    /// return the error type
+    fn type_(&self) -> String {
+        self.err_code().error_type.to_string()
+    }
+
+    /// return the doc url ascociated with the error
+    fn url(&self) -> String {
+        format!("https://docs.meilisearch.com/error/{}", self.name())
+    }
+}
+
+/// Internal structure providing a convenient way to create error codes
+struct ErrCode {
+    status_code: StatusCode,
+    error_type: ErrorType,
+    error_name: &'static str,
+}
+
+impl ErrCode {
+    fn authentication(error_name: &'static str, status_code: StatusCode) -> ErrCode {
+        ErrCode {
+            status_code,
+            error_name,
+            error_type: ErrorType::Authentication,
+        }
+    }
+
+    fn internal(error_name: &'static str, status_code: StatusCode) -> ErrCode {
+        ErrCode {
+            status_code,
+            error_name,
+            error_type: ErrorType::InternalError,
+        }
+    }
+
+    fn invalid(error_name: &'static str, status_code: StatusCode) -> ErrCode {
+        ErrCode {
+            status_code,
+            error_name,
+            error_type: ErrorType::InvalidRequest,
+        }
+    }
+}
diff --git a/meilisearch-http/Cargo.toml b/meilisearch-http/Cargo.toml
index 368c8f649..abcbba9d2 100644
--- a/meilisearch-http/Cargo.toml
+++ b/meilisearch-http/Cargo.toml
@@ -29,12 +29,12 @@ chrono = { version = "0.4.11", features = ["serde"] }
 crossbeam-channel = "0.4.2"
 env_logger = "0.7.1"
 futures = "0.3.4"
-heed = "0.8.0"
 http = "0.1.19"
 indexmap = { version = "1.3.2", features = ["serde-1"] }
 log = "0.4.8"
 main_error = "0.1.0"
 meilisearch-core = { path = "../meilisearch-core", version = "0.10.1" }
+meilisearch-error = { path = "../meilisearch-error", version = "0.10.1" }
 meilisearch-schema = { path = "../meilisearch-schema", version = "0.10.1" }
 meilisearch-tokenizer = {path = "../meilisearch-tokenizer", version = "0.10.1"}
 mime = "0.3.16"
diff --git a/meilisearch-http/src/data.rs b/meilisearch-http/src/data.rs
index 39b7f9b1e..3692b0b69 100644
--- a/meilisearch-http/src/data.rs
+++ b/meilisearch-http/src/data.rs
@@ -1,21 +1,13 @@
-use std::collections::HashMap;
 use std::ops::Deref;
 use std::sync::Arc;
 
-use chrono::{DateTime, Utc};
-use heed::types::{SerdeBincode, Str};
-use log::error;
-use meilisearch_core::{Database, DatabaseOptions, Error as MError, MResult, MainT, UpdateT};
+use meilisearch_core::{Database, DatabaseOptions};
 use sha2::Digest;
 use sysinfo::Pid;
 
 use crate::index_update_callback;
 use crate::option::Opt;
 
-const LAST_UPDATE_KEY: &str = "last-update";
-
-type SerdeDatetime = SerdeBincode<DateTime<Utc>>;
-
 #[derive(Clone)]
 pub struct Data {
     inner: Arc<DataInner>,
@@ -62,72 +54,6 @@ impl ApiKeys {
     }
 }
 
-impl DataInner {
-    pub fn is_indexing(&self, reader: &heed::RoTxn<UpdateT>, index: &str) -> MResult<Option<bool>> {
-        match self.db.open_index(&index) {
-            Some(index) => index.current_update_id(&reader).map(|u| Some(u.is_some())),
-            None => Ok(None),
-        }
-    }
-
-    pub fn last_update(&self, reader: &heed::RoTxn<MainT>) -> MResult<Option<DateTime<Utc>>> {
-        match self
-            .db
-            .common_store()
-            .get::<_, Str, SerdeDatetime>(reader, LAST_UPDATE_KEY)?
-        {
-            Some(datetime) => Ok(Some(datetime)),
-            None => Ok(None),
-        }
-    }
-
-    pub fn set_last_update(&self, writer: &mut heed::RwTxn<MainT>) -> MResult<()> {
-        self.db
-            .common_store()
-            .put::<_, Str, SerdeDatetime>(writer, LAST_UPDATE_KEY, &Utc::now())
-            .map_err(Into::into)
-    }
-
-    pub fn compute_stats(&self, writer: &mut heed::RwTxn<MainT>, index_uid: &str) -> MResult<()> {
-        let index = match self.db.open_index(&index_uid) {
-            Some(index) => index,
-            None => {
-                error!("Impossible to retrieve index {}", index_uid);
-                return Ok(());
-            }
-        };
-
-        let schema = match index.main.schema(&writer)? {
-            Some(schema) => schema,
-            None => return Ok(()),
-        };
-
-        let all_documents_fields = index
-            .documents_fields_counts
-            .all_documents_fields_counts(&writer)?;
-
-        // count fields frequencies
-        let mut fields_distribution = HashMap::<_, usize>::new();
-        for result in all_documents_fields {
-            let (_, attr, _) = result?;
-            if let Some(field_id) = schema.indexed_pos_to_field_id(attr) {
-                *fields_distribution.entry(field_id).or_default() += 1;
-            }
-        }
-
-        // convert attributes to their names
-        let distribution: HashMap<_, _> = fields_distribution
-            .into_iter()
-            .filter_map(|(a, c)| schema.name(a).map(|name| (name.to_string(), c)))
-            .collect();
-
-        index
-            .main
-            .put_fields_distribution(writer, &distribution)
-            .map_err(MError::Zlmdb)
-    }
-}
-
 impl Data {
     pub fn new(opt: Opt) -> Data {
         let db_path = opt.db_path.clone();
diff --git a/meilisearch-http/src/error.rs b/meilisearch-http/src/error.rs
index 27626c80b..3f57e3a92 100644
--- a/meilisearch-http/src/error.rs
+++ b/meilisearch-http/src/error.rs
@@ -1,13 +1,41 @@
+use std::error;
 use std::fmt;
 
 use actix_http::ResponseBuilder;
 use actix_web as aweb;
+use actix_web::error::JsonPayloadError;
 use actix_web::http::StatusCode;
 use serde_json::json;
-use actix_web::error::JsonPayloadError;
+
+use meilisearch_error::{ErrorCode, Code};
 
 #[derive(Debug)]
-pub enum ResponseError {
+pub struct ResponseError {
+    inner: Box<dyn ErrorCode>,
+}
+
+impl error::Error for ResponseError {}
+
+impl ErrorCode for ResponseError {
+    fn error_code(&self) -> Code {
+        self.inner.error_code()
+    }
+}
+
+impl fmt::Display for ResponseError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.inner.fmt(f)
+    }
+}
+
+impl From<Error> for ResponseError {
+    fn from(error: Error) -> ResponseError {
+        ResponseError { inner: Box::new(error) }
+    }
+}
+
+#[derive(Debug)]
+pub enum Error {
     BadParameter(String, String),
     BadRequest(String),
     CreateIndex(String),
@@ -21,15 +49,40 @@ pub enum ResponseError {
     MissingHeader(String),
     NotFound(String),
     OpenIndex(String),
-    FilterParsing(String),
     RetrieveDocument(u32, String),
     SearchDocuments(String),
     PayloadTooLarge,
     UnsupportedMediaType,
-    FacetExpression(String),
-    FacetCount(String),
 }
 
+impl error::Error for Error {}
+
+impl ErrorCode for Error {
+    fn error_code(&self) -> Code {
+        use Error::*;
+        match self {
+            BadParameter(_, _) => Code::BadParameter,
+            BadRequest(_) => Code::BadRequest,
+            CreateIndex(_) => Code::CreateIndex,
+            DocumentNotFound(_) => Code::DocumentNotFound,
+            IndexNotFound(_) => Code::IndexNotFound,
+            Internal(_) => Code::Internal,
+            InvalidIndexUid => Code::InvalidIndexUid,
+            InvalidToken(_) => Code::InvalidToken,
+            Maintenance => Code::Maintenance,
+            MissingAuthorizationHeader => Code::MissingAuthorizationHeader,
+            MissingHeader(_) => Code::MissingHeader,
+            NotFound(_) => Code::NotFound,
+            OpenIndex(_) => Code::OpenIndex,
+            RetrieveDocument(_, _) => Code::RetrieveDocument,
+            SearchDocuments(_) => Code::SearchDocuments,
+            PayloadTooLarge => Code::PayloadTooLarge,
+            UnsupportedMediaType => Code::UnsupportedMediaType,
+        }
+    }
+}
+
+#[derive(Debug)]
 pub enum FacetCountError {
     AttributeNotSet(String),
     SyntaxError(String),
@@ -37,6 +90,14 @@ pub enum FacetCountError {
     NoFacetSet,
 }
 
+impl error::Error for FacetCountError {}
+
+impl ErrorCode for FacetCountError {
+    fn error_code(&self) -> Code {
+        Code::BadRequest
+    }
+}
+
 impl FacetCountError {
     pub fn unexpected_token(found: impl ToString, expected: &'static [&'static str]) -> FacetCountError {
         let found = found.to_string();
@@ -63,69 +124,69 @@ impl fmt::Display for FacetCountError {
     }
 }
 
-impl ResponseError {
-    pub fn internal(err: impl fmt::Display) -> ResponseError {
-        ResponseError::Internal(err.to_string())
+impl Error {
+    pub fn internal(err: impl fmt::Display) -> Error {
+        Error::Internal(err.to_string())
     }
 
-    pub fn bad_request(err: impl fmt::Display) -> ResponseError {
-        ResponseError::BadRequest(err.to_string())
+    pub fn bad_request(err: impl fmt::Display) -> Error {
+        Error::BadRequest(err.to_string())
     }
 
-    pub fn missing_authorization_header() -> ResponseError {
-        ResponseError::MissingAuthorizationHeader
+    pub fn missing_authorization_header() -> Error {
+        Error::MissingAuthorizationHeader
     }
 
-    pub fn invalid_token(err: impl fmt::Display) -> ResponseError {
-        ResponseError::InvalidToken(err.to_string())
+    pub fn invalid_token(err: impl fmt::Display) -> Error {
+        Error::InvalidToken(err.to_string())
     }
 
-    pub fn not_found(err: impl fmt::Display) -> ResponseError {
-        ResponseError::NotFound(err.to_string())
+    pub fn not_found(err: impl fmt::Display) -> Error {
+        Error::NotFound(err.to_string())
     }
 
-    pub fn index_not_found(err: impl fmt::Display) -> ResponseError {
-        ResponseError::IndexNotFound(err.to_string())
+    pub fn index_not_found(err: impl fmt::Display) -> Error {
+        Error::IndexNotFound(err.to_string())
     }
 
-    pub fn document_not_found(err: impl fmt::Display) -> ResponseError {
-        ResponseError::DocumentNotFound(err.to_string())
+    pub fn document_not_found(err: impl fmt::Display) -> Error {
+        Error::DocumentNotFound(err.to_string())
     }
 
-    pub fn missing_header(err: impl fmt::Display) -> ResponseError {
-        ResponseError::MissingHeader(err.to_string())
+    pub fn missing_header(err: impl fmt::Display) -> Error {
+        Error::MissingHeader(err.to_string())
     }
 
-    pub fn bad_parameter(param: impl fmt::Display, err: impl fmt::Display) -> ResponseError {
-        ResponseError::BadParameter(param.to_string(), err.to_string())
+    pub fn bad_parameter(param: impl fmt::Display, err: impl fmt::Display) -> Error {
+        Error::BadParameter(param.to_string(), err.to_string())
     }
 
-    pub fn open_index(err: impl fmt::Display) -> ResponseError {
-        ResponseError::OpenIndex(err.to_string())
+    pub fn open_index(err: impl fmt::Display) -> Error {
+        Error::OpenIndex(err.to_string())
     }
 
-    pub fn create_index(err: impl fmt::Display) -> ResponseError {
-        ResponseError::CreateIndex(err.to_string())
+    pub fn create_index(err: impl fmt::Display) -> Error {
+        Error::CreateIndex(err.to_string())
     }
 
-    pub fn invalid_index_uid() -> ResponseError {
-        ResponseError::InvalidIndexUid
+    pub fn invalid_index_uid() -> Error {
+        Error::InvalidIndexUid
     }
 
-    pub fn maintenance() -> ResponseError {
-        ResponseError::Maintenance
+    pub fn maintenance() -> Error {
+        Error::Maintenance
     }
 
-    pub fn retrieve_document(doc_id: u32, err: impl fmt::Display) -> ResponseError {
-        ResponseError::RetrieveDocument(doc_id, err.to_string())
+    pub fn retrieve_document(doc_id: u32, err: impl fmt::Display) -> Error {
+        Error::RetrieveDocument(doc_id, err.to_string())
     }
 
-    pub fn search_documents(err: impl fmt::Display) -> ResponseError {
-        ResponseError::SearchDocuments(err.to_string())
+    pub fn search_documents(err: impl fmt::Display) -> Error {
+        Error::SearchDocuments(err.to_string())
     }
 }
 
-impl fmt::Display for ResponseError {
+impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::BadParameter(param, err) => write!(f, "Url parameter {} error: {}", param, err),
@@ -137,17 +198,14 @@ impl fmt::Display for ResponseError {
             Self::InvalidIndexUid => f.write_str("Index must have a valid uid; Index uid can be of type integer or string only composed of alphanumeric characters, hyphens (-) and underscores (_)."),
             Self::InvalidToken(err) => write!(f, "Invalid API key: {}", err),
             Self::Maintenance => f.write_str("Server is in maintenance, please try again later"),
-            Self::FilterParsing(err) => write!(f, "parsing error: {}", err),
             Self::MissingAuthorizationHeader => f.write_str("You must have an authorization token"),
             Self::MissingHeader(header) => write!(f, "Header {} is missing", header),
             Self::NotFound(err) => write!(f, "{} not found", err),
             Self::OpenIndex(err) => write!(f, "Impossible to open index; {}", err),
             Self::RetrieveDocument(id, err) => write!(f, "impossible to retrieve the document with id: {}; {}", id, err),
             Self::SearchDocuments(err) => write!(f, "impossible to search documents; {}", err),
-            Self::FacetExpression(e) => write!(f, "error parsing facet filter expression: {}", e),
             Self::PayloadTooLarge => f.write_str("Payload to large"),
             Self::UnsupportedMediaType => f.write_str("Unsupported media type"),
-            Self::FacetCount(e) => write!(f, "error with facet count: {}", e),
         }
     }
 }
@@ -156,101 +214,53 @@ impl aweb::error::ResponseError for ResponseError {
     fn error_response(&self) -> aweb::HttpResponse {
         ResponseBuilder::new(self.status_code()).json(json!({
             "message": self.to_string(),
+            "errorCode": self.error_name(),
+            "errorType": self.error_type(),
+            "errorLink": self.error_url(),
         }))
     }
 
     fn status_code(&self) -> StatusCode {
-       match *self {
-            Self::BadParameter(_, _)
-            | Self::BadRequest(_)
-            | Self::CreateIndex(_)
-            | Self::InvalidIndexUid
-            | Self::OpenIndex(_)
-            | Self::RetrieveDocument(_, _)
-            | Self::FacetExpression(_)
-            | Self::SearchDocuments(_)
-            | Self::FacetCount(_)
-            | Self::FilterParsing(_) => StatusCode::BAD_REQUEST,
-            Self::DocumentNotFound(_)
-            | Self::IndexNotFound(_)
-            | Self::NotFound(_) => StatusCode::NOT_FOUND,
-            Self::InvalidToken(_)
-            | Self::MissingHeader(_) => StatusCode::UNAUTHORIZED,
-            Self::MissingAuthorizationHeader => StatusCode::FORBIDDEN,
-            Self::Internal(_) => StatusCode::INTERNAL_SERVER_ERROR,
-            Self::Maintenance => StatusCode::SERVICE_UNAVAILABLE,
-            Self::PayloadTooLarge => StatusCode::PAYLOAD_TOO_LARGE,
-            Self::UnsupportedMediaType => StatusCode::UNSUPPORTED_MEDIA_TYPE,
-        }
-    }
-}
-
-impl From<meilisearch_core::HeedError> for ResponseError {
-    fn from(err: meilisearch_core::HeedError) -> ResponseError {
-        ResponseError::Internal(err.to_string())
-    }
-}
-
-impl From<meilisearch_core::FstError> for ResponseError {
-    fn from(err: meilisearch_core::FstError) -> ResponseError {
-        ResponseError::Internal(err.to_string())
-    }
-}
-
-impl From<meilisearch_core::FacetError> for ResponseError {
-    fn from(error: meilisearch_core::FacetError) -> ResponseError {
-        ResponseError::FacetExpression(error.to_string())
+        self.http_status()
     }
 }
 
 impl From<meilisearch_core::Error> for ResponseError {
     fn from(err: meilisearch_core::Error) -> ResponseError {
-        use meilisearch_core::pest_error::LineColLocation::*;
-        match err {
-            meilisearch_core::Error::FilterParseError(e) => {
-                let (line, column) = match e.line_col {
-                    Span((line, _), (column, _)) => (line, column),
-                    Pos((line, column)) => (line, column),
-                };
-                let message = format!("parsing error on line {} at column {}: {}", line, column, e.variant.message());
-
-                ResponseError::FilterParsing(message)
-            },
-            meilisearch_core::Error::FacetError(e) => ResponseError::FacetExpression(e.to_string()),
-            _ => ResponseError::Internal(err.to_string()),
-        }
+        ResponseError { inner: Box::new(err) }
     }
 }
 
 impl From<meilisearch_schema::Error> for ResponseError {
     fn from(err: meilisearch_schema::Error) -> ResponseError {
-        ResponseError::Internal(err.to_string())
+        ResponseError { inner: Box::new(err) }
     }
 }
 
-impl From<actix_http::Error> for ResponseError {
-    fn from(err: actix_http::Error) -> ResponseError {
-        ResponseError::Internal(err.to_string())
+impl From<actix_http::Error> for Error {
+    fn from(err: actix_http::Error) -> Error {
+        Error::Internal(err.to_string())
     }
 }
 
 impl From<FacetCountError> for ResponseError {
-    fn from(other: FacetCountError) -> ResponseError {
-        ResponseError::FacetCount(other.to_string())
+    fn from(err: FacetCountError) -> ResponseError {
+        ResponseError { inner: Box::new(err) }
     }
 }
 
-impl From<JsonPayloadError> for ResponseError {
-    fn from(err: JsonPayloadError) -> ResponseError {
+impl From<JsonPayloadError> for Error {
+    fn from(err: JsonPayloadError) -> Error {
         match err {
-            JsonPayloadError::Deserialize(err) => ResponseError::BadRequest(format!("Invalid JSON: {}", err)),
-            JsonPayloadError::Overflow => ResponseError::PayloadTooLarge,
-            JsonPayloadError::ContentType => ResponseError::UnsupportedMediaType,
-            JsonPayloadError::Payload(err) => ResponseError::BadRequest(format!("Problem while decoding the request: {}", err)),
+            JsonPayloadError::Deserialize(err) => Error::BadRequest(format!("Invalid JSON: {}", err)),
+            JsonPayloadError::Overflow => Error::PayloadTooLarge,
+            JsonPayloadError::ContentType => Error::UnsupportedMediaType,
+            JsonPayloadError::Payload(err) => Error::BadRequest(format!("Problem while decoding the request: {}", err)),
         }
     }
 }
 
 pub fn json_error_handler(err: JsonPayloadError) -> ResponseError {
-    err.into()
+    let error = Error::from(err);
+    error.into()
 }
diff --git a/meilisearch-http/src/helpers/authentication.rs b/meilisearch-http/src/helpers/authentication.rs
index 894718d53..927665ffe 100644
--- a/meilisearch-http/src/helpers/authentication.rs
+++ b/meilisearch-http/src/helpers/authentication.rs
@@ -4,10 +4,10 @@ use std::rc::Rc;
 use std::task::{Context, Poll};
 
 use actix_service::{Service, Transform};
-use actix_web::{dev::ServiceRequest, dev::ServiceResponse, Error};
+use actix_web::{dev::ServiceRequest, dev::ServiceResponse};
 use futures::future::{err, ok, Future, Ready};
 
-use crate::error::ResponseError;
+use crate::error::{Error, ResponseError};
 use crate::Data;
 
 #[derive(Clone)]
@@ -19,13 +19,13 @@ pub enum Authentication {
 
 impl<S: 'static, B> Transform<S> for Authentication
 where
-    S: Service<Request = ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
+    S: Service<Request = ServiceRequest, Response = ServiceResponse<B>, Error = actix_web::Error>,
     S::Future: 'static,
     B: 'static,
 {
     type Request = ServiceRequest;
     type Response = ServiceResponse<B>;
-    type Error = Error;
+    type Error = actix_web::Error;
     type InitError = ();
     type Transform = LoggingMiddleware<S>;
     type Future = Ready<Result<Self::Transform, Self::InitError>>;
@@ -45,13 +45,13 @@ pub struct LoggingMiddleware<S> {
 
 impl<S, B> Service for LoggingMiddleware<S>
 where
-    S: Service<Request = ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
+    S: Service<Request = ServiceRequest, Response = ServiceResponse<B>, Error = actix_web::Error> + 'static,
     S::Future: 'static,
     B: 'static,
 {
     type Request = ServiceRequest;
     type Response = ServiceResponse<B>;
-    type Error = Error;
+    type Error = actix_web::Error;
     type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
 
     fn poll_ready(&mut self, cx: &mut Context) -> Poll<Result<(), Self::Error>> {
@@ -71,10 +71,10 @@ where
         let auth_header = match req.headers().get("X-Meili-API-Key") {
             Some(auth) => match auth.to_str() {
                 Ok(auth) => auth,
-                Err(_) => return Box::pin(err(ResponseError::MissingAuthorizationHeader.into())),
+                Err(_) => return Box::pin(err(ResponseError::from(Error::MissingAuthorizationHeader).into())),
             },
             None => {
-                return Box::pin(err(ResponseError::MissingAuthorizationHeader.into()));
+                return Box::pin(err(ResponseError::from(Error::MissingAuthorizationHeader).into()));
             }
         };
 
@@ -95,7 +95,7 @@ where
             Box::pin(svc.call(req))
         } else {
             Box::pin(err(
-                ResponseError::InvalidToken(auth_header.to_string()).into()
+                ResponseError::from(Error::InvalidToken(auth_header.to_string())).into()
             ))
         }
     }
diff --git a/meilisearch-http/src/helpers/meilisearch.rs b/meilisearch-http/src/helpers/meilisearch.rs
index b6ae2c6b8..65b6da08f 100644
--- a/meilisearch-http/src/helpers/meilisearch.rs
+++ b/meilisearch-http/src/helpers/meilisearch.rs
@@ -5,11 +5,11 @@ use std::time::Instant;
 
 use indexmap::IndexMap;
 use log::error;
-use meilisearch_core::Filter;
+use meilisearch_core::{Filter, MainReader};
 use meilisearch_core::facets::FacetFilter;
 use meilisearch_core::criterion::*;
 use meilisearch_core::settings::RankingRule;
-use meilisearch_core::{Highlight, Index, MainT, RankedMap};
+use meilisearch_core::{Highlight, Index, RankedMap};
 use meilisearch_schema::{FieldId, Schema};
 use meilisearch_tokenizer::is_cjk;
 use serde::{Deserialize, Serialize};
@@ -17,7 +17,7 @@ use serde_json::Value;
 use siphasher::sip::SipHasher;
 use slice_group_by::GroupBy;
 
-use crate::error::ResponseError;
+use crate::error::{Error, ResponseError};
 
 pub trait IndexSearchExt {
     fn new_search(&self, query: String) -> SearchBuilder;
@@ -107,12 +107,12 @@ impl<'a> SearchBuilder<'a> {
         self
     }
 
-    pub fn search(self, reader: &heed::RoTxn<MainT>) -> Result<SearchResult, ResponseError> {
+    pub fn search(self, reader: &MainReader) -> Result<SearchResult, ResponseError> {
         let schema = self
             .index
             .main
             .schema(reader)?
-            .ok_or(ResponseError::internal("missing schema"))?;
+            .ok_or(Error::internal("missing schema"))?;
 
         let ranked_map = self.index.main.ranked_map(reader)?.unwrap_or_default();
 
@@ -159,7 +159,7 @@ impl<'a> SearchBuilder<'a> {
 
         let start = Instant::now();
         let result = query_builder.query(reader, &self.query, self.offset..(self.offset + self.limit));
-        let search_result = result.map_err(ResponseError::search_documents)?;
+        let search_result = result.map_err(Error::search_documents)?;
         let time_ms = start.elapsed().as_millis() as usize;
 
         let mut all_attributes: HashSet<&str> = HashSet::new();
@@ -194,8 +194,8 @@ impl<'a> SearchBuilder<'a> {
             let mut document: IndexMap<String, Value> = self
                 .index
                 .document(reader, Some(&all_attributes), doc.id)
-                .map_err(|e| ResponseError::retrieve_document(doc.id.0, e))?
-                .ok_or(ResponseError::internal(
+                .map_err(|e| Error::retrieve_document(doc.id.0, e))?
+                .ok_or(Error::internal(
                     "Impossible to retrieve the document; Corrupted data",
                 ))?;
 
@@ -257,7 +257,7 @@ impl<'a> SearchBuilder<'a> {
 
     pub fn get_criteria(
         &self,
-        reader: &heed::RoTxn<MainT>,
+        reader: &MainReader,
         ranked_map: &'a RankedMap,
         schema: &Schema,
     ) -> Result<Option<Criteria<'a>>, ResponseError> {
diff --git a/meilisearch-http/src/lib.rs b/meilisearch-http/src/lib.rs
index e2e24d4d2..8e81d9221 100644
--- a/meilisearch-http/src/lib.rs
+++ b/meilisearch-http/src/lib.rs
@@ -7,14 +7,17 @@ pub mod models;
 pub mod option;
 pub mod routes;
 
-pub use self::data::Data;
-use self::error::json_error_handler;
 use actix_http::Error;
 use actix_service::ServiceFactory;
 use actix_web::{dev, web, App};
+use chrono::Utc;
 use log::error;
+
 use meilisearch_core::ProcessedUpdateResult;
 
+pub use self::data::Data;
+use self::error::{json_error_handler, ResponseError};
+
 pub fn create_app(
     data: &Data,
 ) -> App<
@@ -55,28 +58,23 @@ pub fn index_update_callback(index_uid: &str, data: &Data, status: ProcessedUpda
 
     if let Some(index) = data.db.open_index(&index_uid) {
         let db = &data.db;
-        let mut writer = match db.main_write_txn() {
-            Ok(writer) => writer,
-            Err(e) => {
-                error!("Impossible to get write_txn; {}", e);
-                return;
+        let res = db.main_write::<_, _, ResponseError>(|mut writer| {
+            if let Err(e) = data.db.compute_stats(&mut writer, &index_uid) {
+                error!("Impossible to compute stats; {}", e)
             }
-        };
 
-        if let Err(e) = data.compute_stats(&mut writer, &index_uid) {
-            error!("Impossible to compute stats; {}", e)
-        }
+            if let Err(e) = data.db.set_last_update(&mut writer, &Utc::now()) {
+                error!("Impossible to update last_update; {}", e)
+            }
 
-        if let Err(e) = data.set_last_update(&mut writer) {
-            error!("Impossible to update last_update; {}", e)
-        }
-
-        if let Err(e) = index.main.put_updated_at(&mut writer) {
-            error!("Impossible to update updated_at; {}", e)
-        }
-
-        if let Err(e) = writer.commit() {
-            error!("Impossible to get write_txn; {}", e);
+            if let Err(e) = index.main.put_updated_at(&mut writer) {
+                error!("Impossible to update updated_at; {}", e)
+            }
+            Ok(())
+        });
+        match res {
+            Ok(_) => (),
+            Err(e) => error!("{}", e),
         }
     }
 }
diff --git a/meilisearch-http/src/routes/document.rs b/meilisearch-http/src/routes/document.rs
index eca88a590..e7ad3801b 100644
--- a/meilisearch-http/src/routes/document.rs
+++ b/meilisearch-http/src/routes/document.rs
@@ -7,10 +7,10 @@ use meilisearch_core::update;
 use serde::Deserialize;
 use serde_json::Value;
 
-use crate::error::ResponseError;
+use crate::Data;
+use crate::error::{Error, ResponseError};
 use crate::helpers::Authentication;
 use crate::routes::{IndexParam, IndexUpdateResponse};
-use crate::Data;
 
 type Document = IndexMap<String, Value>;
 
@@ -41,18 +41,19 @@ async fn get_document(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let reader = data.db.main_read_txn()?;
+
     let internal_id = index.main
         .external_to_internal_docid(&reader, &path.document_id)?
-        .ok_or(ResponseError::document_not_found(&path.document_id))?;
+        .ok_or(Error::document_not_found(&path.document_id))?;
 
-    let response: Document = index
+    let document: Document = index
         .document(&reader, None, internal_id)?
-        .ok_or(ResponseError::document_not_found(&path.document_id))?;
+        .ok_or(Error::document_not_found(&path.document_id))?;
 
-    Ok(HttpResponse::Ok().json(response))
+    Ok(HttpResponse::Ok().json(document))
 }
 
 #[delete(
@@ -66,16 +67,12 @@ async fn delete_document(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
-
-    let mut update_writer = data.db.update_write_txn()?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let mut documents_deletion = index.documents_deletion();
     documents_deletion.delete_document_by_external_docid(path.document_id.clone());
 
-    let update_id = documents_deletion.finalize(&mut update_writer)?;
-
-    update_writer.commit()?;
+    let update_id = data.db.update_write(|w| documents_deletion.finalize(w))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -97,13 +94,12 @@ async fn get_all_documents(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let offset = params.offset.unwrap_or(0);
     let limit = params.limit.unwrap_or(20);
 
     let reader = data.db.main_read_txn()?;
-
     let documents_ids: Result<BTreeSet<_>, _> = index
         .documents_fields_counts
         .documents_ids(&reader)?
@@ -111,23 +107,21 @@ async fn get_all_documents(
         .take(limit)
         .collect();
 
-    let documents_ids = documents_ids?;
-
     let attributes: Option<HashSet<&str>> = params
         .attributes_to_retrieve
         .as_ref()
         .map(|a| a.split(',').collect());
 
-    let mut response = Vec::new();
-    for document_id in documents_ids {
+    let mut documents = Vec::new();
+    for document_id in documents_ids? {
         if let Ok(Some(document)) =
             index.document::<Document>(&reader, attributes.as_ref(), document_id)
         {
-            response.push(document);
+            documents.push(document);
         }
     }
 
-    Ok(HttpResponse::Ok().json(response))
+    Ok(HttpResponse::Ok().json(documents))
 }
 
 fn find_primary_key(document: &IndexMap<String, Value>) -> Option<String> {
@@ -155,14 +149,14 @@ async fn update_multiple_documents(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let reader = data.db.main_read_txn()?;
 
     let mut schema = index
         .main
         .schema(&reader)?
-        .ok_or(ResponseError::internal("Impossible to retrieve the schema"))?;
+        .ok_or(Error::internal("Impossible to retrieve the schema"))?;
 
     if schema.primary_key().is_none() {
         let id = match &params.primary_key {
@@ -170,16 +164,14 @@ async fn update_multiple_documents(
             None => body
                 .first()
                 .and_then(find_primary_key)
-                .ok_or(ResponseError::bad_request("Could not infer a primary key"))?,
+                .ok_or(Error::bad_request("Could not infer a primary key"))?,
         };
 
-        let mut writer = data.db.main_write_txn()?;
-
         schema
             .set_primary_key(&id)
-            .map_err(ResponseError::bad_request)?;
-        index.main.put_schema(&mut writer, &schema)?;
-        writer.commit()?;
+            .map_err(Error::bad_request)?;
+
+        data.db.main_write(|w| index.main.put_schema(w, &schema))?;
     }
 
     let mut document_addition = if is_partial {
@@ -192,9 +184,7 @@ async fn update_multiple_documents(
         document_addition.update_document(document);
     }
 
-    let mut update_writer = data.db.update_write_txn()?;
-    let update_id = document_addition.finalize(&mut update_writer)?;
-    update_writer.commit()?;
+    let update_id = data.db.update_write(|w| document_addition.finalize(w))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -231,9 +221,8 @@ async fn delete_documents(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
-    let mut writer = data.db.update_write_txn()?;
 
     let mut documents_deletion = index.documents_deletion();
 
@@ -242,9 +231,7 @@ async fn delete_documents(
         documents_deletion.delete_document_by_external_docid(document_id);
     }
 
-    let update_id = documents_deletion.finalize(&mut writer)?;
-
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| documents_deletion.finalize(w))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -257,13 +244,9 @@ async fn clear_all_documents(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
-    let mut writer = data.db.update_write_txn()?;
-
-    let update_id = index.clear_all(&mut writer)?;
-
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.clear_all(w))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
diff --git a/meilisearch-http/src/routes/health.rs b/meilisearch-http/src/routes/health.rs
index 826e8ee02..0f0a3a203 100644
--- a/meilisearch-http/src/routes/health.rs
+++ b/meilisearch-http/src/routes/health.rs
@@ -1,14 +1,11 @@
 use actix_web::{web, HttpResponse};
 use actix_web_macros::{get, put};
-use heed::types::{Str, Unit};
 use serde::Deserialize;
 
-use crate::error::ResponseError;
+use crate::error::{Error, ResponseError};
 use crate::helpers::Authentication;
 use crate::Data;
 
-const UNHEALTHY_KEY: &str = "_is_unhealthy";
-
 pub fn services(cfg: &mut web::ServiceConfig) {
     cfg.service(get_health).service(change_healthyness);
 }
@@ -16,31 +13,19 @@ pub fn services(cfg: &mut web::ServiceConfig) {
 #[get("/health", wrap = "Authentication::Private")]
 async fn get_health(data: web::Data<Data>) -> Result<HttpResponse, ResponseError> {
     let reader = data.db.main_read_txn()?;
-
-    let common_store = data.db.common_store();
-
-    if let Ok(Some(_)) = common_store.get::<_, Str, Unit>(&reader, UNHEALTHY_KEY) {
-        return Err(ResponseError::Maintenance);
+    if let Ok(Some(_)) = data.db.get_health(&reader) {
+        return Err(Error::Maintenance.into());
     }
-
     Ok(HttpResponse::Ok().finish())
 }
 
 async fn set_healthy(data: web::Data<Data>) -> Result<HttpResponse, ResponseError> {
-    let mut writer = data.db.main_write_txn()?;
-    let common_store = data.db.common_store();
-    common_store.delete::<_, Str>(&mut writer, UNHEALTHY_KEY)?;
-    writer.commit()?;
-
+    data.db.main_write(|w| data.db.set_healthy(w))?;
     Ok(HttpResponse::Ok().finish())
 }
 
 async fn set_unhealthy(data: web::Data<Data>) -> Result<HttpResponse, ResponseError> {
-    let mut writer = data.db.main_write_txn()?;
-    let common_store = data.db.common_store();
-    common_store.put::<_, Str, Unit>(&mut writer, UNHEALTHY_KEY, &())?;
-    writer.commit()?;
-
+    data.db.main_write(|w| data.db.set_unhealthy(w))?;
     Ok(HttpResponse::Ok().finish())
 }
 
diff --git a/meilisearch-http/src/routes/index.rs b/meilisearch-http/src/routes/index.rs
index d43967bdd..f12179902 100644
--- a/meilisearch-http/src/routes/index.rs
+++ b/meilisearch-http/src/routes/index.rs
@@ -5,7 +5,7 @@ use log::error;
 use rand::seq::SliceRandom;
 use serde::{Deserialize, Serialize};
 
-use crate::error::ResponseError;
+use crate::error::{Error, ResponseError};
 use crate::helpers::Authentication;
 use crate::routes::IndexParam;
 use crate::Data;
@@ -42,28 +42,27 @@ struct IndexResponse {
 #[get("/indexes", wrap = "Authentication::Private")]
 async fn list_indexes(data: web::Data<Data>) -> Result<HttpResponse, ResponseError> {
     let reader = data.db.main_read_txn()?;
-
-    let mut response = Vec::new();
+    let mut indexes = Vec::new();
 
     for index_uid in data.db.indexes_uids() {
         let index = data.db.open_index(&index_uid);
 
         match index {
             Some(index) => {
-                let name = index.main.name(&reader)?.ok_or(ResponseError::internal(
-                    "Impossible to get the name of an index",
+                let name = index.main.name(&reader)?.ok_or(Error::internal(
+                        "Impossible to get the name of an index",
                 ))?;
                 let created_at = index
                     .main
                     .created_at(&reader)?
-                    .ok_or(ResponseError::internal(
-                        "Impossible to get the create date of an index",
+                    .ok_or(Error::internal(
+                            "Impossible to get the create date of an index",
                     ))?;
                 let updated_at = index
                     .main
                     .updated_at(&reader)?
-                    .ok_or(ResponseError::internal(
-                        "Impossible to get the last update date of an index",
+                    .ok_or(Error::internal(
+                            "Impossible to get the last update date of an index",
                     ))?;
 
                 let primary_key = match index.main.schema(&reader) {
@@ -81,7 +80,7 @@ async fn list_indexes(data: web::Data<Data>) -> Result<HttpResponse, ResponseErr
                     updated_at,
                     primary_key,
                 };
-                response.push(index_response);
+                indexes.push(index_response);
             }
             None => error!(
                 "Index {} is referenced in the indexes list but cannot be found",
@@ -90,7 +89,7 @@ async fn list_indexes(data: web::Data<Data>) -> Result<HttpResponse, ResponseErr
         }
     }
 
-    Ok(HttpResponse::Ok().json(response))
+    Ok(HttpResponse::Ok().json(indexes))
 }
 
 #[get("/indexes/{index_uid}", wrap = "Authentication::Private")]
@@ -101,24 +100,23 @@ async fn get_index(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let reader = data.db.main_read_txn()?;
-
-    let name = index.main.name(&reader)?.ok_or(ResponseError::internal(
-        "Impossible to get the name of an index",
+    let name = index.main.name(&reader)?.ok_or(Error::internal(
+            "Impossible to get the name of an index",
     ))?;
     let created_at = index
         .main
         .created_at(&reader)?
-        .ok_or(ResponseError::internal(
-            "Impossible to get the create date of an index",
+        .ok_or(Error::internal(
+                "Impossible to get the create date of an index",
         ))?;
     let updated_at = index
         .main
         .updated_at(&reader)?
-        .ok_or(ResponseError::internal(
-            "Impossible to get the last update date of an index",
+        .ok_or(Error::internal(
+                "Impossible to get the last update date of an index",
         ))?;
 
     let primary_key = match index.main.schema(&reader) {
@@ -128,14 +126,15 @@ async fn get_index(
         },
         _ => None,
     };
-
-    Ok(HttpResponse::Ok().json(IndexResponse {
+    let index_response = IndexResponse {
         name,
         uid: path.index_uid.clone(),
         created_at,
         updated_at,
         primary_key,
-    }))
+    };
+
+    Ok(HttpResponse::Ok().json(index_response))
 }
 
 #[derive(Debug, Deserialize)]
@@ -152,9 +151,9 @@ async fn create_index(
     body: web::Json<IndexCreateRequest>,
 ) -> Result<HttpResponse, ResponseError> {
     if let (None, None) = (body.name.clone(), body.uid.clone()) {
-        return Err(ResponseError::bad_request(
+        return Err(Error::bad_request(
             "Index creation must have an uid",
-        ));
+        ).into());
     }
 
     let uid = match &body.uid {
@@ -165,7 +164,7 @@ async fn create_index(
             {
                 uid.to_owned()
             } else {
-                return Err(ResponseError::InvalidIndexUid);
+                return Err(Error::InvalidIndexUid.into());
             }
         }
         None => loop {
@@ -179,41 +178,41 @@ async fn create_index(
     let created_index = data
         .db
         .create_index(&uid)
-        .map_err(ResponseError::create_index)?;
+        .map_err(Error::create_index)?;
 
-    let mut writer = data.db.main_write_txn()?;
+    let index_response = data.db.main_write::<_, _, ResponseError>(|mut writer| {
+        let name = body.name.as_ref().unwrap_or(&uid);
+        created_index.main.put_name(&mut writer, name)?;
 
-    let name = body.name.as_ref().unwrap_or(&uid);
-    created_index.main.put_name(&mut writer, name)?;
+        let created_at = created_index
+            .main
+            .created_at(&writer)?
+            .ok_or(Error::internal("Impossible to read created at"))?;
 
-    let created_at = created_index
-        .main
-        .created_at(&writer)?
-        .ok_or(ResponseError::internal("Impossible to read created at"))?;
+        let updated_at = created_index
+            .main
+            .updated_at(&writer)?
+            .ok_or(Error::internal("Impossible to read updated at"))?;
 
-    let updated_at = created_index
-        .main
-        .updated_at(&writer)?
-        .ok_or(ResponseError::internal("Impossible to read updated at"))?;
-
-    if let Some(id) = body.primary_key.clone() {
-        if let Some(mut schema) = created_index.main.schema(&writer)? {
-            schema
-                .set_primary_key(&id)
-                .map_err(ResponseError::bad_request)?;
-            created_index.main.put_schema(&mut writer, &schema)?;
+        if let Some(id) = body.primary_key.clone() {
+            if let Some(mut schema) = created_index.main.schema(&writer)? {
+                schema
+                    .set_primary_key(&id)
+                    .map_err(Error::bad_request)?;
+                created_index.main.put_schema(&mut writer, &schema)?;
+            }
         }
-    }
+        let index_response = IndexResponse {
+            name: name.to_string(),
+            uid,
+            created_at,
+            updated_at,
+            primary_key: body.primary_key.clone(),
+        };
+        Ok(index_response)
+    })?;
 
-    writer.commit()?;
-
-    Ok(HttpResponse::Created().json(IndexResponse {
-        name: name.to_string(),
-        uid,
-        created_at,
-        updated_at,
-        primary_key: body.primary_key.clone(),
-    }))
+    Ok(HttpResponse::Created().json(index_response))
 }
 
 #[derive(Debug, Deserialize)]
@@ -242,49 +241,47 @@ async fn update_index(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
-    let mut writer = data.db.main_write_txn()?;
+    data.db.main_write::<_, _, ResponseError>(|writer| {
+        if let Some(name) = &body.name {
+            index.main.put_name(writer, name)?;
+        }
 
-    if let Some(name) = &body.name {
-        index.main.put_name(&mut writer, name)?;
-    }
-
-    if let Some(id) = body.primary_key.clone() {
-        if let Some(mut schema) = index.main.schema(&writer)? {
-            match schema.primary_key() {
-                Some(_) => {
-                    return Err(ResponseError::bad_request(
-                        "The primary key cannot be updated",
-                    ));
-                }
-                None => {
-                    schema.set_primary_key(&id)?;
-                    index.main.put_schema(&mut writer, &schema)?;
+        if let Some(id) = body.primary_key.clone() {
+            if let Some(mut schema) = index.main.schema(writer)? {
+                match schema.primary_key() {
+                    Some(_) => {
+                        return Err(Error::bad_request(
+                                "The primary key cannot be updated",
+                        ).into());
+                    }
+                    None => {
+                        schema.set_primary_key(&id)?;
+                        index.main.put_schema(writer, &schema)?;
+                    }
                 }
             }
         }
-    }
-
-    index.main.put_updated_at(&mut writer)?;
-    writer.commit()?;
+        index.main.put_updated_at(writer)?;
+        Ok(())
+    })?;
 
     let reader = data.db.main_read_txn()?;
-
-    let name = index.main.name(&reader)?.ok_or(ResponseError::internal(
-        "Impossible to get the name of an index",
+    let name = index.main.name(&reader)?.ok_or(Error::internal(
+            "Impossible to get the name of an index",
     ))?;
     let created_at = index
         .main
         .created_at(&reader)?
-        .ok_or(ResponseError::internal(
-            "Impossible to get the create date of an index",
+        .ok_or(Error::internal(
+                "Impossible to get the create date of an index",
         ))?;
     let updated_at = index
         .main
         .updated_at(&reader)?
-        .ok_or(ResponseError::internal(
-            "Impossible to get the last update date of an index",
+        .ok_or(Error::internal(
+                "Impossible to get the last update date of an index",
         ))?;
 
     let primary_key = match index.main.schema(&reader) {
@@ -295,13 +292,15 @@ async fn update_index(
         _ => None,
     };
 
-    Ok(HttpResponse::Ok().json(IndexResponse {
+    let index_response = IndexResponse {
         name,
         uid: path.index_uid.clone(),
         created_at,
         updated_at,
         primary_key,
-    }))
+    };
+
+    Ok(HttpResponse::Ok().json(index_response))
 }
 
 #[delete("/indexes/{index_uid}", wrap = "Authentication::Private")]
@@ -331,7 +330,7 @@ async fn get_update_status(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let reader = data.db.update_read_txn()?;
 
@@ -339,10 +338,10 @@ async fn get_update_status(
 
     match status {
         Some(status) => Ok(HttpResponse::Ok().json(status)),
-        None => Err(ResponseError::NotFound(format!(
+        None => Err(Error::NotFound(format!(
             "Update {} not found",
             path.update_id
-        ))),
+        )).into()),
     }
 }
 
@@ -354,7 +353,7 @@ async fn get_all_updates_status(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let reader = data.db.update_read_txn()?;
 
diff --git a/meilisearch-http/src/routes/search.rs b/meilisearch-http/src/routes/search.rs
index 2bc7b45d0..1a2521386 100644
--- a/meilisearch-http/src/routes/search.rs
+++ b/meilisearch-http/src/routes/search.rs
@@ -7,7 +7,7 @@ use actix_web_macros::get;
 use serde::Deserialize;
 use serde_json::Value;
 
-use crate::error::{ResponseError, FacetCountError};
+use crate::error::{Error, FacetCountError, ResponseError};
 use crate::helpers::meilisearch::IndexSearchExt;
 use crate::helpers::Authentication;
 use crate::routes::IndexParam;
@@ -45,14 +45,13 @@ async fn search_with_url_query(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let reader = data.db.main_read_txn()?;
-
     let schema = index
         .main
         .schema(&reader)?
-        .ok_or(ResponseError::internal("Impossible to retrieve the schema"))?;
+        .ok_or(Error::internal("Impossible to retrieve the schema"))?;
 
     let mut search_builder = index.new_search(params.q.clone());
 
@@ -88,9 +87,9 @@ async fn search_with_url_query(
     }
 
     if let Some(ref facet_filters) = params.facet_filters {
-        match index.main.attributes_for_faceting(&reader)? {
-            Some(ref attrs) => { search_builder.add_facet_filters(FacetFilter::from_str(facet_filters, &schema, attrs)?); },
-            None => return Err(ResponseError::FacetExpression("can't filter on facets, as no facet is set".to_string()))
+        let attrs = index.main.attributes_for_faceting(&reader)?;
+        if let Some(attrs) = attrs {
+            search_builder.add_facet_filters(FacetFilter::from_str(facet_filters, &schema, &attrs)?);
         }
     }
 
@@ -100,7 +99,7 @@ async fn search_with_url_query(
                 let field_ids = prepare_facet_list(&facets, &schema, attrs)?;
                 search_builder.add_facets(field_ids);
             },
-            None => return Err(FacetCountError::NoFacetSet.into())
+            None => return Err(FacetCountError::NoFacetSet.into()),
         }
     }
 
@@ -160,8 +159,9 @@ async fn search_with_url_query(
             search_builder.get_matches();
         }
     }
+    let search_result = search_builder.search(&reader)?;
 
-    Ok(HttpResponse::Ok().json(search_builder.search(&reader)?))
+    Ok(HttpResponse::Ok().json(search_result))
 }
 
 /// Parses the incoming string into an array of attributes for which to return a count. It returns
diff --git a/meilisearch-http/src/routes/setting.rs b/meilisearch-http/src/routes/setting.rs
index 04ed8ceed..c7abd6ce4 100644
--- a/meilisearch-http/src/routes/setting.rs
+++ b/meilisearch-http/src/routes/setting.rs
@@ -3,7 +3,7 @@ use actix_web_macros::{delete, get, post};
 use meilisearch_core::settings::{Settings, SettingsUpdate, UpdateState, DEFAULT_RANKING_RULES};
 use std::collections::{BTreeMap, BTreeSet, HashSet};
 
-use crate::error::ResponseError;
+use crate::error::{Error, ResponseError};
 use crate::helpers::Authentication;
 use crate::routes::{IndexParam, IndexUpdateResponse};
 use crate::Data;
@@ -37,15 +37,16 @@ async fn update_all(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
-    let mut writer = data.db.update_write_txn()?;
-    let settings = body
-        .into_inner()
-        .into_update()
-        .map_err(ResponseError::bad_request)?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let update_id = data.db.update_write::<_, _, ResponseError>(|writer| {
+        let settings = body
+            .into_inner()
+            .into_update()
+            .map_err(Error::bad_request)?;
+        let update_id = index.settings_update(writer, settings)?;
+        Ok(update_id)
+    })?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -58,22 +59,22 @@ async fn get_all(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let reader = data.db.main_read_txn()?;
 
-    let stop_words_fst = index.main.stop_words_fst(&reader)?;
-    let stop_words = stop_words_fst.stream().into_strs()?;
-    let stop_words: BTreeSet<String> = stop_words.into_iter().collect();
+    let stop_words: BTreeSet<String> = index
+        .main
+        .stop_words(&reader)?
+        .into_iter()
+        .collect();
 
-    let synonyms_fst = index.main.synonyms_fst(&reader)?;
-    let synonyms_list = synonyms_fst.stream().into_strs()?;
+    let synonyms_list = index.main.synonyms(&reader)?;
 
     let mut synonyms = BTreeMap::new();
     let index_synonyms = &index.synonyms;
     for synonym in synonyms_list {
-        let alternative_list = index_synonyms.synonyms(&reader, synonym.as_bytes())?;
-        let list = alternative_list.stream().into_strs()?;
+        let list = index_synonyms.synonyms(&reader, synonym.as_bytes())?;
         synonyms.insert(synonym, list);
     }
 
@@ -138,8 +139,7 @@ async fn delete_all(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
-    let mut writer = data.db.update_write_txn()?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = SettingsUpdate {
         ranking_rules: UpdateState::Clear,
@@ -153,8 +153,7 @@ async fn delete_all(
         attributes_for_faceting: UpdateState::Clear,
     };
 
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -170,7 +169,7 @@ async fn get_rules(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
     let reader = data.db.main_read_txn()?;
 
     let ranking_rules = index
@@ -196,17 +195,15 @@ async fn update_rules(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = Settings {
         ranking_rules: Some(body.into_inner()),
         ..Settings::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let settings = settings.into_update().map_err(ResponseError::bad_request)?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let settings = settings.into_update().map_err(Error::bad_request)?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -222,17 +219,14 @@ async fn delete_rules(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
-    let mut writer = data.db.update_write_txn()?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = SettingsUpdate {
         ranking_rules: UpdateState::Clear,
         ..SettingsUpdate::default()
     };
 
-    let update_id = index.settings_update(&mut writer, settings)?;
-
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -248,7 +242,7 @@ async fn get_distinct(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
     let reader = data.db.main_read_txn()?;
     let distinct_attribute = index.main.distinct_attribute(&reader)?;
 
@@ -267,17 +261,15 @@ async fn update_distinct(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = Settings {
         distinct_attribute: Some(body.into_inner()),
         ..Settings::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let settings = settings.into_update().map_err(ResponseError::bad_request)?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let settings = settings.into_update().map_err(Error::bad_request)?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -293,17 +285,14 @@ async fn delete_distinct(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
-    let mut writer = data.db.update_write_txn()?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = SettingsUpdate {
         distinct_attribute: UpdateState::Clear,
         ..SettingsUpdate::default()
     };
 
-    let update_id = index.settings_update(&mut writer, settings)?;
-
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -319,7 +308,7 @@ async fn get_searchable(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
     let reader = data.db.main_read_txn()?;
     let schema = index.main.schema(&reader)?;
     let searchable_attributes: Option<Vec<String>> =
@@ -340,17 +329,16 @@ async fn update_searchable(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = Settings {
         searchable_attributes: Some(body.into_inner()),
         ..Settings::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let settings = settings.into_update().map_err(ResponseError::bad_request)?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let settings = settings.into_update().map_err(Error::bad_request)?;
+
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -366,16 +354,14 @@ async fn delete_searchable(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = SettingsUpdate {
         searchable_attributes: UpdateState::Clear,
         ..SettingsUpdate::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -391,7 +377,7 @@ async fn get_displayed(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
     let reader = data.db.main_read_txn()?;
 
     let schema = index.main.schema(&reader)?;
@@ -414,17 +400,15 @@ async fn update_displayed(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = Settings {
         displayed_attributes: Some(body.into_inner()),
         ..Settings::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let settings = settings.into_update().map_err(ResponseError::bad_request)?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let settings = settings.into_update().map_err(Error::bad_request)?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -440,16 +424,14 @@ async fn delete_displayed(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = SettingsUpdate {
         displayed_attributes: UpdateState::Clear,
         ..SettingsUpdate::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -465,7 +447,7 @@ async fn get_accept_new_fields(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
     let reader = data.db.main_read_txn()?;
 
     let schema = index.main.schema(&reader)?;
@@ -487,17 +469,15 @@ async fn update_accept_new_fields(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = Settings {
         accept_new_fields: Some(body.into_inner()),
         ..Settings::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let settings = settings.into_update().map_err(ResponseError::bad_request)?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let settings = settings.into_update().map_err(Error::bad_request)?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
diff --git a/meilisearch-http/src/routes/stats.rs b/meilisearch-http/src/routes/stats.rs
index 6c31283cd..5f3e09dd5 100644
--- a/meilisearch-http/src/routes/stats.rs
+++ b/meilisearch-http/src/routes/stats.rs
@@ -10,7 +10,7 @@ use serde::Serialize;
 use sysinfo::{NetworkExt, ProcessExt, ProcessorExt, System, SystemExt};
 use walkdir::WalkDir;
 
-use crate::error::ResponseError;
+use crate::error::{Error, ResponseError};
 use crate::helpers::Authentication;
 use crate::routes::IndexParam;
 use crate::Data;
@@ -39,7 +39,7 @@ async fn index_stats(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let reader = data.db.main_read_txn()?;
 
@@ -50,8 +50,8 @@ async fn index_stats(
     let update_reader = data.db.update_read_txn()?;
 
     let is_indexing =
-        data.is_indexing(&update_reader, &path.index_uid)?
-            .ok_or(ResponseError::internal(
+        data.db.is_indexing(&update_reader, &path.index_uid)?
+            .ok_or(Error::internal(
                 "Impossible to know if the database is indexing",
             ))?;
 
@@ -86,8 +86,8 @@ async fn get_stats(data: web::Data<Data>) -> Result<HttpResponse, ResponseError>
 
                 let fields_distribution = index.main.fields_distribution(&reader)?.unwrap_or_default();
 
-                let is_indexing = data.is_indexing(&update_reader, &index_uid)?.ok_or(
-                    ResponseError::internal("Impossible to know if the database is indexing"),
+                let is_indexing = data.db.is_indexing(&update_reader, &index_uid)?.ok_or(
+                    Error::internal("Impossible to know if the database is indexing"),
                 )?;
 
                 let response = IndexStatsResponse {
@@ -111,7 +111,7 @@ async fn get_stats(data: web::Data<Data>) -> Result<HttpResponse, ResponseError>
         .filter(|metadata| metadata.is_file())
         .fold(0, |acc, m| acc + m.len());
 
-    let last_update = data.last_update(&reader)?;
+    let last_update = data.db.last_update(&reader)?;
 
     Ok(HttpResponse::Ok().json(StatsResult {
         database_size,
diff --git a/meilisearch-http/src/routes/stop_words.rs b/meilisearch-http/src/routes/stop_words.rs
index 90814e423..eaea22827 100644
--- a/meilisearch-http/src/routes/stop_words.rs
+++ b/meilisearch-http/src/routes/stop_words.rs
@@ -3,7 +3,7 @@ use actix_web_macros::{delete, get, post};
 use meilisearch_core::settings::{SettingsUpdate, UpdateState};
 use std::collections::BTreeSet;
 
-use crate::error::ResponseError;
+use crate::error::{Error, ResponseError};
 use crate::helpers::Authentication;
 use crate::routes::{IndexParam, IndexUpdateResponse};
 use crate::Data;
@@ -23,10 +23,9 @@ async fn get(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
     let reader = data.db.main_read_txn()?;
-    let stop_words_fst = index.main.stop_words_fst(&reader)?;
-    let stop_words = stop_words_fst.stream().into_strs()?;
+    let stop_words = index.main.stop_words(&reader)?;
 
     Ok(HttpResponse::Ok().json(stop_words))
 }
@@ -43,16 +42,14 @@ async fn update(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = SettingsUpdate {
         stop_words: UpdateState::Update(body.into_inner()),
         ..SettingsUpdate::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -68,16 +65,14 @@ async fn delete(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = SettingsUpdate {
         stop_words: UpdateState::Clear,
         ..SettingsUpdate::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
diff --git a/meilisearch-http/src/routes/synonym.rs b/meilisearch-http/src/routes/synonym.rs
index 6c9e77f6d..f047e9dd3 100644
--- a/meilisearch-http/src/routes/synonym.rs
+++ b/meilisearch-http/src/routes/synonym.rs
@@ -5,7 +5,7 @@ use actix_web_macros::{delete, get, post};
 use indexmap::IndexMap;
 use meilisearch_core::settings::{SettingsUpdate, UpdateState};
 
-use crate::error::ResponseError;
+use crate::error::{Error, ResponseError};
 use crate::helpers::Authentication;
 use crate::routes::{IndexParam, IndexUpdateResponse};
 use crate::Data;
@@ -25,18 +25,16 @@ async fn get(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let reader = data.db.main_read_txn()?;
 
-    let synonyms_fst = index.main.synonyms_fst(&reader)?;
-    let synonyms_list = synonyms_fst.stream().into_strs()?;
+    let synonyms_list = index.main.synonyms(&reader)?;
 
     let mut synonyms = IndexMap::new();
     let index_synonyms = &index.synonyms;
     for synonym in synonyms_list {
-        let alternative_list = index_synonyms.synonyms(&reader, synonym.as_bytes())?;
-        let list = alternative_list.stream().into_strs()?;
+        let list = index_synonyms.synonyms(&reader, synonym.as_bytes())?;
         synonyms.insert(synonym, list);
     }
 
@@ -55,16 +53,14 @@ async fn update(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = SettingsUpdate {
         synonyms: UpdateState::Update(body.into_inner()),
         ..SettingsUpdate::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
@@ -80,17 +76,14 @@ async fn delete(
     let index = data
         .db
         .open_index(&path.index_uid)
-        .ok_or(ResponseError::index_not_found(&path.index_uid))?;
+        .ok_or(Error::index_not_found(&path.index_uid))?;
 
     let settings = SettingsUpdate {
         synonyms: UpdateState::Clear,
         ..SettingsUpdate::default()
     };
 
-    let mut writer = data.db.update_write_txn()?;
-    let update_id = index.settings_update(&mut writer, settings)?;
-
-    writer.commit()?;
+    let update_id = data.db.update_write(|w| index.settings_update(w, settings))?;
 
     Ok(HttpResponse::Accepted().json(IndexUpdateResponse::with_id(update_id)))
 }
diff --git a/meilisearch-http/tests/documents_delete.rs b/meilisearch-http/tests/documents_delete.rs
index 7edc9ac63..cd0bfc142 100644
--- a/meilisearch-http/tests/documents_delete.rs
+++ b/meilisearch-http/tests/documents_delete.rs
@@ -14,7 +14,7 @@ async fn delete() {
     assert_eq!(status_code, 404);
 }
 
-// Resolve teh issue https://github.com/meilisearch/MeiliSearch/issues/493
+// Resolve the issue https://github.com/meilisearch/MeiliSearch/issues/493
 #[actix_rt::test]
 async fn delete_batch() {
     let mut server = common::Server::with_uid("movies");
diff --git a/meilisearch-http/tests/index.rs b/meilisearch-http/tests/index.rs
index 6ea81f606..ed67f2d1d 100644
--- a/meilisearch-http/tests/index.rs
+++ b/meilisearch-http/tests/index.rs
@@ -382,7 +382,7 @@ async fn create_index_failed() {
 
     assert_eq!(status_code, 400);
     let message = res_value["message"].as_str().unwrap();
-    assert_eq!(res_value.as_object().unwrap().len(), 1);
+    assert_eq!(res_value.as_object().unwrap().len(), 4);
     assert_eq!(message, "Index creation must have an uid");
 
     // 3 - Create a index with extra data
@@ -462,7 +462,7 @@ async fn create_index_with_invalid_uid() {
 
     assert_eq!(status_code, 400);
     let message = response["message"].as_str().unwrap();
-    assert_eq!(response.as_object().unwrap().len(), 1);
+    assert_eq!(response.as_object().unwrap().len(), 4);
     assert_eq!(message, "Index must have a valid uid; Index uid can be of type integer or string only composed of alphanumeric characters, hyphens (-) and underscores (_).");
 
     // 2 - Create the index with invalid uid
@@ -475,7 +475,7 @@ async fn create_index_with_invalid_uid() {
 
     assert_eq!(status_code, 400);
     let message = response["message"].as_str().unwrap();
-    assert_eq!(response.as_object().unwrap().len(), 1);
+    assert_eq!(response.as_object().unwrap().len(), 4);
     assert_eq!(message, "Index must have a valid uid; Index uid can be of type integer or string only composed of alphanumeric characters, hyphens (-) and underscores (_).");
 
     // 3 - Create the index with invalid uid
@@ -488,7 +488,7 @@ async fn create_index_with_invalid_uid() {
 
     assert_eq!(status_code, 400);
     let message = response["message"].as_str().unwrap();
-    assert_eq!(response.as_object().unwrap().len(), 1);
+    assert_eq!(response.as_object().unwrap().len(), 4);
     assert_eq!(message, "Index must have a valid uid; Index uid can be of type integer or string only composed of alphanumeric characters, hyphens (-) and underscores (_).");
 
     // 4 - Create the index with invalid uid
@@ -501,7 +501,7 @@ async fn create_index_with_invalid_uid() {
 
     assert_eq!(status_code, 400);
     let message = response["message"].as_str().unwrap();
-    assert_eq!(response.as_object().unwrap().len(), 1);
+    assert_eq!(response.as_object().unwrap().len(), 4);
     assert_eq!(message, "Index must have a valid uid; Index uid can be of type integer or string only composed of alphanumeric characters, hyphens (-) and underscores (_).");
 }
 
@@ -645,12 +645,10 @@ async fn check_add_documents_without_primary_key() {
 
     let (response, status_code) = server.add_or_replace_multiple_documents_sync(body).await;
 
-    let expected = json!({
-        "message": "Could not infer a primary key"
-    });
-
+    let message = response["message"].as_str().unwrap();
+    assert_eq!(response.as_object().unwrap().len(), 4);
+    assert_eq!(message, "Could not infer a primary key");
     assert_eq!(status_code, 400);
-    assert_json_eq!(response, expected, ordered: false);
 }
 
 #[actix_rt::test]
diff --git a/meilisearch-schema/Cargo.toml b/meilisearch-schema/Cargo.toml
index 712fdb008..a795fa1db 100644
--- a/meilisearch-schema/Cargo.toml
+++ b/meilisearch-schema/Cargo.toml
@@ -8,6 +8,7 @@ edition = "2018"
 [dependencies]
 bincode = "1.2.1"
 indexmap = { version = "1.3.2", features = ["serde-1"] }
+meilisearch-error = { path = "../meilisearch-error", version = "0.10.1" }
 serde = { version = "1.0.105", features = ["derive"] }
 serde_json = { version = "1.0.50", features = ["preserve_order"] }
 toml = { version = "0.5.6", features = ["preserve_order"] }
diff --git a/meilisearch-schema/src/error.rs b/meilisearch-schema/src/error.rs
index c31596df2..8dcc0a7a4 100644
--- a/meilisearch-schema/src/error.rs
+++ b/meilisearch-schema/src/error.rs
@@ -1,6 +1,7 @@
-
 use std::{error, fmt};
 
+use meilisearch_error::{ErrorCode, Code};
+
 pub type SResult<T> = Result<T, Error>;
 
 #[derive(Debug)]
@@ -22,3 +23,15 @@ impl fmt::Display for Error {
 }
 
 impl error::Error for Error {}
+
+impl ErrorCode for Error {
+    fn error_code(&self) -> Code {
+        use Error::*;
+
+        match self {
+            FieldNameNotFound(_) => Code::Internal,
+            MaxFieldsLimitExceeded => Code::MaxFieldsLimitExceeded,
+            PrimaryKeyAlreadyPresent => Code::PrimaryKeyAlreadyPresent,
+        }
+    }
+}