diff --git a/meilisearch-core/src/database.rs b/meilisearch-core/src/database.rs
index 22c7c7d56..0b0cd3149 100644
--- a/meilisearch-core/src/database.rs
+++ b/meilisearch-core/src/database.rs
@@ -11,13 +11,20 @@ use heed::CompactionOption;
 use log::{debug, error};
 use meilisearch_schema::Schema;
 
-use crate::{store, update, Index, MResult, Error, UpdateReader, UpdateWriter, MainReader, MainWriter};
+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";
 
@@ -427,8 +434,7 @@ impl Database {
 
     pub fn last_update(&self, reader: &heed::RoTxn<MainT>) -> MResult<Option<DateTime<Utc>>> {
         match self.common_store()
-            .get::<_, Str, SerdeDatetime>(reader, LAST_UPDATE_KEY)?
-            {
+            .get::<_, Str, SerdeDatetime>(reader, LAST_UPDATE_KEY)? {
                 Some(datetime) => Ok(Some(datetime)),
                 None => Ok(None),
             }
@@ -492,7 +498,7 @@ impl Database {
 
         index
             .main
-            .put_fields_frequency(writer, &frequency)
+            .put_fields_distribution(writer, &frequency)
     }
 }
 
@@ -1223,4 +1229,3 @@ mod tests {
         assert_matches!(iter.next(), None);
     }
 }
-
diff --git a/meilisearch-core/src/lib.rs b/meilisearch-core/src/lib.rs
index d837bae62..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};
@@ -52,12 +52,6 @@ use crate::reordered_attrs::ReorderedAttrs;
 type FstSetCow<'a> = fst::Set<Cow<'a, [u8]>>;
 type FstMapCow<'a> = fst::Map<Cow<'a, [u8]>>;
 
-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>;
-
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
 pub struct Document {
     pub id: DocumentId,
diff --git a/meilisearch-core/src/store/main.rs b/meilisearch-core/src/store/main.rs
index 21b506307..f1ef6fc5e 100644
--- a/meilisearch-core/src/store/main.rs
+++ b/meilisearch-core/src/store/main.rs
@@ -197,7 +197,7 @@ impl Main {
         }
     }
 
-    pub fn synonyms_list(self, reader: &heed::RoTxn<MainT>) -> MResult<Vec<String>> {
+    pub fn synonyms(self, reader: &heed::RoTxn<MainT>) -> MResult<Vec<String>> {
         let synonyms = self
             .synonyms_fst(&reader)?
             .stream()
@@ -217,7 +217,7 @@ impl Main {
         }
     }
 
-    pub fn stop_words_list(self, reader: &heed::RoTxn<MainT>) -> MResult<Vec<String>> {
+    pub fn stop_words(self, reader: &heed::RoTxn<MainT>) -> MResult<Vec<String>> {
         let stop_word_list = self
             .stop_words_fst(reader)?
             .stream()
@@ -249,7 +249,7 @@ impl Main {
         writer: &mut heed::RwTxn<MainT>,
         fields_frequency: &FreqsMap,
     ) -> MResult<()> {
-        Ok(self.main.put::<_, Str, SerdeFreqsMap>(writer, FIELDS_FREQUENCY_KEY, fields_frequency)?)
+        Ok(self.main.put::<_, Str, SerdeFreqsMap>(writer, FIELDS_DISTRIBUTION_KEY, fields_frequency)?)
     }
 
     pub fn fields_distribution(&self, reader: &heed::RoTxn<MainT>) -> MResult<Option<FreqsMap>> {
diff --git a/meilisearch-core/src/store/synonyms.rs b/meilisearch-core/src/store/synonyms.rs
index 699667fcd..bf7472f96 100644
--- a/meilisearch-core/src/store/synonyms.rs
+++ b/meilisearch-core/src/store/synonyms.rs
@@ -27,7 +27,7 @@ impl Synonyms {
         self.synonyms.clear(writer)
     }
 
-    pub fn synonyms_fst<'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()),
@@ -42,4 +42,3 @@ impl Synonyms {
         Ok(synonyms)
     }
 }
-
diff --git a/meilisearch-error/Cargo.toml b/meilisearch-error/Cargo.toml
index 1be97bdb8..ad77978b1 100644
--- a/meilisearch-error/Cargo.toml
+++ b/meilisearch-error/Cargo.toml
@@ -1,10 +1,8 @@
 [package]
 name = "meilisearch-error"
 version = "0.10.1"
-authors = ["mpostma <postma.marin@protonmail.com>"]
+authors = ["marin <postma.marin@protonmail.com>"]
 edition = "2018"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
 [dependencies]
 actix-http = "1.0.1"
diff --git a/meilisearch-error/src/lib.rs b/meilisearch-error/src/lib.rs
index 63f94f655..66838ed02 100644
--- a/meilisearch-error/src/lib.rs
+++ b/meilisearch-error/src/lib.rs
@@ -57,12 +57,11 @@ pub enum Code {
     MissingPrimaryKey,
     PrimaryKeyAlreadyPresent,
 
-    // invalid documents FIXME make one error code?
-    MissingDocumentId,
     MaxFieldsLimitExceeded,
+    MissingDocumentId,
 
-    Filter,
     Facet,
+    Filter,
 
     BadParameter,
     BadRequest,
@@ -73,9 +72,9 @@ pub enum Code {
     MissingAuthorizationHeader,
     MissingHeader,
     NotFound,
+    PayloadTooLarge,
     RetrieveDocument,
     SearchDocuments,
-    PayloadTooLarge,
     UnsupportedMediaType,
     Other,
 }
@@ -90,8 +89,7 @@ impl Code {
             // 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),
+            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
@@ -101,24 +99,24 @@ impl Code {
             PrimaryKeyAlreadyPresent => ErrCode::internal("primary_key_already_present", StatusCode::INTERNAL_SERVER_ERROR),
 
             // invalid document
-            MissingDocumentId => ErrCode::invalid("MissingDocumentId", StatusCode::BAD_REQUEST),
             MaxFieldsLimitExceeded => ErrCode::invalid("max_field_limit_exceeded", StatusCode::BAD_REQUEST),
+            MissingDocumentId => ErrCode::invalid("missing_document_id", StatusCode::BAD_REQUEST),
 
-            Filter => ErrCode::invalid("fitler", StatusCode::BAD_REQUEST),
-            Facet => ErrCode::invalid("facet", 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),
-            RetrieveDocument => ErrCode::invalid("retrieve_document", StatusCode::BAD_REQUEST),
-            SearchDocuments => ErrCode::invalid("search_document", StatusCode::BAD_REQUEST),
-            DocumentNotFound => ErrCode::invalid("document_not_found", StatusCode::NOT_FOUND),
-            NotFound => ErrCode::invalid("not_found", StatusCode::NOT_FOUND),
-            InvalidToken => ErrCode::authentication("invalid_token", StatusCode::UNAUTHORIZED),
-            MissingHeader => ErrCode::authentication("missing_header", StatusCode::UNAUTHORIZED),
-            MissingAuthorizationHeader => ErrCode::authentication("missing_authorization_header", StatusCode::FORBIDDEN),
+            DocumentNotFound => ErrCode::internal("document_not_found", StatusCode::NOT_FOUND),
             Internal => ErrCode::internal("internal", StatusCode::INTERNAL_SERVER_ERROR),
-            Maintenance =>  ErrCode::invalid("maintenance", StatusCode::SERVICE_UNAVAILABLE),
+            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),
             _ => ErrCode::invalid("other", StatusCode::BAD_REQUEST),
         }
@@ -131,12 +129,12 @@ impl Code {
 
     /// return error name, used as error code
     fn name(&self) -> String {
-        self.err_code().err_name.to_string()
+        self.err_code().error_name.to_string()
     }
 
     /// return the error type
     fn r#type(&self) -> String {
-        self.err_code().err_type.to_string()
+        self.err_code().error_type.to_string()
     }
 
     /// return the doc url ascociated with the error
@@ -148,8 +146,8 @@ impl Code {
 /// Internal structure providing a convenient way to create error codes
 struct ErrCode {
     status_code: StatusCode,
-    err_type: ErrorType,
-    err_name: &'static str,
+    error_type: ErrorType,
+    error_name: &'static str,
 }
 
 impl ErrCode {
@@ -157,24 +155,24 @@ impl ErrCode {
     fn authentication(err_name: &'static str, status_code: StatusCode) -> ErrCode {
         ErrCode {
             status_code,
-            err_name,
-            err_type: ErrorType::Authentication,
+            error_name: err_name,
+            error_type: ErrorType::Authentication,
         }
     }
 
     fn internal(err_name: &'static str, status_code: StatusCode) -> ErrCode {
         ErrCode {
             status_code,
-            err_name,
-            err_type: ErrorType::InternalError,
+            error_name: err_name,
+            error_type: ErrorType::InternalError,
         }
     }
 
     fn invalid(err_name: &'static str, status_code: StatusCode) -> ErrCode {
         ErrCode {
             status_code,
-            err_name,
-            err_type: ErrorType::InvalidRequest,
+            error_name: err_name,
+            error_type: ErrorType::InvalidRequest,
         }
     }
 }
diff --git a/meilisearch-http/src/data.rs b/meilisearch-http/src/data.rs
index 15c2ff1af..3692b0b69 100644
--- a/meilisearch-http/src/data.rs
+++ b/meilisearch-http/src/data.rs
@@ -96,4 +96,3 @@ impl Data {
         data
     }
 }
-
diff --git a/meilisearch-http/src/error.rs b/meilisearch-http/src/error.rs
index 606b54b65..3f57e3a92 100644
--- a/meilisearch-http/src/error.rs
+++ b/meilisearch-http/src/error.rs
@@ -1,11 +1,11 @@
-use std::fmt;
 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};
 
diff --git a/meilisearch-http/src/routes/document.rs b/meilisearch-http/src/routes/document.rs
index c97bc7b28..448d04562 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::Data;
 use crate::error::{Error, ResponseError};
 use crate::helpers::Authentication;
 use crate::routes::{IndexParam, IndexUpdateResponse};
-use crate::Data;
 
 type Document = IndexMap<String, Value>;
 
@@ -192,7 +192,7 @@ async fn update_multiple_documents(
 
     let update_id = data
         .db
-        .update_write::<_, _, ResponseError>(move |writer| {
+        .update_write::<_, _, ResponseError>(|writer| {
             let update_id = document_addition.finalize(writer)?;
             Ok(update_id)
         })?;
diff --git a/meilisearch-http/src/routes/health.rs b/meilisearch-http/src/routes/health.rs
index d0114d8c5..c6f33b6fb 100644
--- a/meilisearch-http/src/routes/health.rs
+++ b/meilisearch-http/src/routes/health.rs
@@ -24,6 +24,7 @@ async fn set_healthy(data: web::Data<Data>) -> Result<HttpResponse, ResponseErro
         data.db.set_healthy(writer)?;
         Ok(())
     })?;
+    
     Ok(HttpResponse::Ok().finish())
 }
 
@@ -32,6 +33,7 @@ async fn set_unhealthy(data: web::Data<Data>) -> Result<HttpResponse, ResponseEr
         data.db.set_unhealthy(writer)?;
         Ok(())
     })?;
+    
     Ok(HttpResponse::Ok().finish())
 }
 
diff --git a/meilisearch-http/src/routes/setting.rs b/meilisearch-http/src/routes/setting.rs
index de4a9fa9e..6bb883ee8 100644
--- a/meilisearch-http/src/routes/setting.rs
+++ b/meilisearch-http/src/routes/setting.rs
@@ -65,11 +65,11 @@ async fn get_all(
 
     let stop_words: BTreeSet<String> = index
         .main
-        .stop_words_list(&reader)?
+        .stop_words(&reader)?
         .into_iter()
         .collect();
 
-    let synonyms_list = index.main.synonyms_list(&reader)?;
+    let synonyms_list = index.main.synonyms(&reader)?;
 
     let mut synonyms = BTreeMap::new();
     let index_synonyms = &index.synonyms;
diff --git a/meilisearch-http/src/routes/stop_words.rs b/meilisearch-http/src/routes/stop_words.rs
index 092ca9b2a..0c22cbd13 100644
--- a/meilisearch-http/src/routes/stop_words.rs
+++ b/meilisearch-http/src/routes/stop_words.rs
@@ -25,7 +25,7 @@ async fn get(
         .open_index(&path.index_uid)
         .ok_or(Error::index_not_found(&path.index_uid))?;
     let reader = data.db.main_read_txn()?;
-    let stop_words = index.main.stop_words_list(&reader)?;
+    let stop_words = index.main.stop_words(&reader)?;
 
     Ok(HttpResponse::Ok().json(stop_words))
 }
diff --git a/meilisearch-http/src/routes/synonym.rs b/meilisearch-http/src/routes/synonym.rs
index 0b1867126..169230adb 100644
--- a/meilisearch-http/src/routes/synonym.rs
+++ b/meilisearch-http/src/routes/synonym.rs
@@ -29,7 +29,7 @@ async fn get(
 
     let reader = data.db.main_read_txn()?;
 
-    let synonyms_list = index.main.synonyms_list(&reader)?;
+    let synonyms_list = index.main.synonyms(&reader)?;
 
     let mut synonyms = IndexMap::new();
     let index_synonyms = &index.synonyms;