diff --git a/crates/milli/src/update/facet/mod.rs b/crates/milli/src/update/facet/mod.rs
index 44f499f8c..02b6e7649 100644
--- a/crates/milli/src/update/facet/mod.rs
+++ b/crates/milli/src/update/facet/mod.rs
@@ -101,6 +101,7 @@ use crate::{try_split_array_at, FieldId, Index, Result};
 
 pub mod bulk;
 pub mod incremental;
+pub mod new_incremental;
 
 /// A builder used to add new elements to the `facet_id_string_docids` or `facet_id_f64_docids` databases.
 ///
diff --git a/crates/milli/src/update/facet/new_incremental.rs b/crates/milli/src/update/facet/new_incremental.rs
new file mode 100644
index 000000000..57358888e
--- /dev/null
+++ b/crates/milli/src/update/facet/new_incremental.rs
@@ -0,0 +1,469 @@
+use std::ops::Bound;
+
+use heed::types::{Bytes, DecodeIgnore};
+use heed::{BytesDecode as _, Database, RwTxn};
+use roaring::RoaringBitmap;
+
+use crate::facet::FacetType;
+use crate::heed_codec::facet::{
+    FacetGroupKey, FacetGroupKeyCodec, FacetGroupValue, FacetGroupValueCodec,
+};
+use crate::heed_codec::BytesRefCodec;
+use crate::search::facet::get_highest_level;
+use crate::update::valid_facet_value;
+use crate::{FieldId, Index, Result};
+
+pub struct FacetsUpdateIncremental {
+    inner: FacetsUpdateIncrementalInner,
+    delta_data: Vec<FacetFieldIdChange>,
+}
+
+struct FacetsUpdateIncrementalInner {
+    db: Database<FacetGroupKeyCodec<BytesRefCodec>, FacetGroupValueCodec>,
+    field_id: FieldId,
+    group_size: u8,
+    min_level_size: u8,
+    max_group_size: u8,
+}
+
+impl FacetsUpdateIncremental {
+    pub fn new(
+        index: &Index,
+        facet_type: FacetType,
+        field_id: FieldId,
+        delta_data: Vec<FacetFieldIdChange>,
+        group_size: u8,
+        min_level_size: u8,
+        max_group_size: u8,
+    ) -> Self {
+        FacetsUpdateIncremental {
+            inner: FacetsUpdateIncrementalInner {
+                db: match facet_type {
+                    FacetType::String => index
+                        .facet_id_string_docids
+                        .remap_key_type::<FacetGroupKeyCodec<BytesRefCodec>>(),
+                    FacetType::Number => index
+                        .facet_id_f64_docids
+                        .remap_key_type::<FacetGroupKeyCodec<BytesRefCodec>>(),
+                },
+                field_id,
+                group_size,
+                min_level_size,
+                max_group_size,
+            },
+
+            delta_data,
+        }
+    }
+
+    #[tracing::instrument(level = "trace", skip_all, target = "indexing::facets::incremental")]
+    pub fn execute(mut self, wtxn: &mut RwTxn) -> Result<()> {
+        if self.delta_data.is_empty() {
+            return Ok(());
+        }
+        self.delta_data.sort_unstable_by(
+            |FacetFieldIdChange { facet_value: left, .. },
+             FacetFieldIdChange { facet_value: right, .. }| left.cmp(right),
+        );
+
+        self.inner.find_touched_parents(
+            wtxn,
+            0,
+            self.delta_data
+                .into_iter()
+                // reverse lexicographic order
+                .rev()
+                .map(|change| change.facet_value.into()),
+        )?;
+
+        self.inner.add_or_delete_level(wtxn)
+    }
+}
+
+impl FacetsUpdateIncrementalInner {
+    /// WARNING: `touched_children` must be sorted in **reverse** lexicographic order.
+    fn find_touched_parents(
+        &self,
+        wtxn: &mut RwTxn,
+        child_level: u8,
+        mut touched_children: impl Iterator<Item = Vec<u8>>,
+    ) -> Result<()> {
+        let mut touched_parents = vec![];
+        let Some(parent_level) = child_level.checked_add(1) else { return Ok(()) };
+        let parent_level_left_bound: FacetGroupKey<&[u8]> =
+            FacetGroupKey { field_id: self.field_id, level: parent_level, left_bound: &[] };
+
+        let mut last_parent: Option<Vec<u8>> = None;
+
+        for child in &mut touched_children {
+            if !valid_facet_value(&child) {
+                continue;
+            }
+
+            if let Some(last_parent) = &last_parent {
+                if child.as_slice() >= last_parent.as_slice() {
+                    self.compute_parent_group(wtxn, child_level, child)?;
+                    continue;
+                }
+            }
+
+            // need to find a new parent
+            let parent_key_prefix = FacetGroupKey {
+                field_id: self.field_id,
+                level: parent_level,
+                left_bound: child.as_slice(),
+            };
+
+            let parent = self
+                .db
+                .remap_data_type::<DecodeIgnore>()
+                .rev_range(
+                    wtxn,
+                    &(
+                        Bound::Excluded(&parent_level_left_bound),
+                        Bound::Included(&parent_key_prefix),
+                    ),
+                )?
+                .next();
+
+            match parent {
+                Some(Ok((parent_key, _parent_value))) => {
+                    // found parent, cache it for next keys
+                    last_parent = Some(parent_key.left_bound.to_owned());
+
+                    // add to modified list for parent level
+                    touched_parents.push(parent_key.left_bound.to_owned());
+                    self.compute_parent_group(wtxn, child_level, child)?;
+                }
+                Some(Err(err)) => return Err(err.into()),
+                None => {
+                    self.compute_parent_group(wtxn, child_level, child)?;
+                    break;
+                }
+            }
+        }
+        // do we have children without parents?
+        if let Some(child) = touched_children.next() {
+            // no parent for that key
+            let mut it = self
+                .db
+                .remap_data_type::<DecodeIgnore>()
+                .prefix_iter_mut(wtxn, &parent_level_left_bound)?;
+            match it.next() {
+                // 1. left of the current left bound, or
+                Some(Ok((first_key, _first_value))) => 'change_left_bound: {
+                    // make sure we don't spill on the neighboring fid (level also included defensively)
+                    if first_key.field_id != self.field_id || first_key.level != parent_level {
+                        break 'change_left_bound;
+                    }
+                    // remove old left bound
+                    unsafe { it.del_current()? };
+                    drop(it);
+                    // pop all elements and order to visit the new left bound
+                    touched_parents.push(child.clone());
+                    self.compute_parent_group(wtxn, child_level, child)?;
+                    for child in touched_children {
+                        let new_left_bound = touched_parents.last_mut().unwrap();
+                        new_left_bound.clear();
+                        new_left_bound.extend_from_slice(&child);
+                        self.compute_parent_group(wtxn, child_level, child)?;
+                    }
+                }
+                Some(Err(err)) => return Err(err.into()),
+                // 2. max level reached, exit
+                None => {
+                    drop(it);
+                    self.compute_parent_group(wtxn, child_level, child)?;
+                    for child in touched_children {
+                        self.compute_parent_group(wtxn, child_level, child)?;
+                    }
+                }
+            }
+        }
+        self.find_touched_parents(
+            wtxn,
+            parent_level,
+            touched_parents
+                // no need to `rev` here because the parents were already visited in reverse order
+                .into_iter(),
+        )
+    }
+
+    fn compute_parent_group(
+        &self,
+        wtxn: &mut RwTxn<'_>,
+        parent_level: u8,
+        parent_left_bound: Vec<u8>,
+    ) -> Result<()> {
+        let mut range_left_bound = parent_left_bound;
+        if parent_level == 0 {
+            return Ok(());
+        }
+        let child_level = parent_level - 1;
+
+        let parent_key = FacetGroupKey {
+            field_id: self.field_id,
+            level: parent_level,
+            left_bound: range_left_bound.as_slice(),
+        };
+        let child_right_bound = self
+            .db
+            .remap_data_type::<DecodeIgnore>()
+            .get_greater_than(wtxn, &parent_key)?
+            .and_then(
+                |(
+                    FacetGroupKey {
+                        level: right_level,
+                        field_id: right_fid,
+                        left_bound: right_bound,
+                    },
+                    _,
+                )| {
+                    if parent_level != right_level || self.field_id != right_fid {
+                        // there was a greater key, but with a greater level or fid, so not a sibling to the parent: ignore
+                        return None;
+                    }
+                    Some(right_bound.to_owned())
+                },
+            );
+        let child_right_bound = match &child_right_bound {
+            Some(right_bound) => Bound::Excluded(FacetGroupKey {
+                left_bound: right_bound.as_slice(),
+                field_id: self.field_id,
+                level: child_level,
+            }),
+            None => Bound::Unbounded,
+        };
+
+        let child_left_key = FacetGroupKey {
+            field_id: self.field_id,
+            level: child_level,
+            left_bound: range_left_bound.as_slice(),
+        };
+        let mut child_left_bound = Bound::Included(child_left_key);
+
+        loop {
+            let mut child_it = self.db.range(wtxn, &(child_left_bound, child_right_bound))?;
+            let res: Result<_> = child_it
+                .by_ref()
+                .take(self.max_group_size as usize)
+                // stop if we go to the next level or field id
+                .take_while(|res| match res {
+                    Ok((child_key, _)) => {
+                        child_key.field_id == self.field_id && child_key.level == child_level
+                    }
+                    Err(_) => true,
+                })
+                .try_fold(
+                    (None, FacetGroupValue { size: 0, bitmap: Default::default() }),
+                    |(bounds, mut group_value), child_res| {
+                        let (child_key, child_value) = child_res?;
+                        let bounds = match bounds {
+                            Some((left_bound, _)) => Some((left_bound, child_key.left_bound)),
+                            None => Some((child_key.left_bound, child_key.left_bound)),
+                        };
+                        // max_group_size <= u8::MAX
+                        group_value.size += 1;
+                        group_value.bitmap |= &child_value.bitmap;
+                        Ok((bounds, group_value))
+                    },
+                );
+
+            let (bounds, group_value) = res?;
+
+            let Some((group_left_bound, right_bound)) = bounds else {
+                let update_key = FacetGroupKey {
+                    field_id: self.field_id,
+                    level: parent_level,
+                    left_bound: range_left_bound.as_slice(),
+                };
+                drop(child_it);
+                if let Bound::Included(_) = child_left_bound {
+                    self.db.delete(wtxn, &update_key)?;
+                }
+
+                break;
+            };
+
+            drop(child_it);
+            let current_left_bound = group_left_bound.to_owned();
+
+            let delete_old_bound = match child_left_bound {
+                Bound::Included(bound) => {
+                    if bound.left_bound != current_left_bound {
+                        Some(range_left_bound.clone())
+                    } else {
+                        None
+                    }
+                }
+                _ => None,
+            };
+
+            range_left_bound.clear();
+            range_left_bound.extend_from_slice(right_bound);
+            let child_left_key = FacetGroupKey {
+                field_id: self.field_id,
+                level: child_level,
+                left_bound: range_left_bound.as_slice(),
+            };
+            child_left_bound = Bound::Excluded(child_left_key);
+
+            if let Some(old_bound) = delete_old_bound {
+                let update_key = FacetGroupKey {
+                    field_id: self.field_id,
+                    level: parent_level,
+                    left_bound: old_bound.as_slice(),
+                };
+                self.db.delete(wtxn, &update_key)?;
+            }
+
+            let update_key = FacetGroupKey {
+                field_id: self.field_id,
+                level: parent_level,
+                left_bound: current_left_bound.as_slice(),
+            };
+            if group_value.bitmap.is_empty() {
+                self.db.delete(wtxn, &update_key)?;
+            } else {
+                self.db.put(wtxn, &update_key, &group_value)?;
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Check whether the highest level has exceeded `min_level_size` * `self.group_size`.
+    /// If it has, we must build an addition level above it.
+    /// Then check whether the highest level is under `min_level_size`.
+    /// If it has, we must remove the complete level.
+    pub(crate) fn add_or_delete_level(&self, txn: &mut RwTxn<'_>) -> Result<()> {
+        let highest_level = get_highest_level(txn, self.db, self.field_id)?;
+        let mut highest_level_prefix = vec![];
+        highest_level_prefix.extend_from_slice(&self.field_id.to_be_bytes());
+        highest_level_prefix.push(highest_level);
+
+        let size_highest_level =
+            self.db.remap_types::<Bytes, Bytes>().prefix_iter(txn, &highest_level_prefix)?.count();
+
+        if size_highest_level >= self.group_size as usize * self.min_level_size as usize {
+            self.add_level(txn, highest_level, &highest_level_prefix, size_highest_level)
+        } else if size_highest_level < self.min_level_size as usize && highest_level != 0 {
+            self.delete_level(txn, &highest_level_prefix)
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Delete a level.
+    fn delete_level(&self, txn: &mut RwTxn<'_>, highest_level_prefix: &[u8]) -> Result<()> {
+        let mut to_delete = vec![];
+        let mut iter =
+            self.db.remap_types::<Bytes, Bytes>().prefix_iter(txn, highest_level_prefix)?;
+        for el in iter.by_ref() {
+            let (k, _) = el?;
+            to_delete.push(
+                FacetGroupKeyCodec::<BytesRefCodec>::bytes_decode(k)
+                    .map_err(heed::Error::Encoding)?
+                    .into_owned(),
+            );
+        }
+        drop(iter);
+        for k in to_delete {
+            self.db.delete(txn, &k.as_ref())?;
+        }
+        Ok(())
+    }
+
+    /// Build an additional level for the field id.
+    fn add_level(
+        &self,
+        txn: &mut RwTxn<'_>,
+        highest_level: u8,
+        highest_level_prefix: &[u8],
+        size_highest_level: usize,
+    ) -> Result<()> {
+        let mut groups_iter = self
+            .db
+            .remap_types::<Bytes, FacetGroupValueCodec>()
+            .prefix_iter(txn, highest_level_prefix)?;
+
+        let nbr_new_groups = size_highest_level / self.group_size as usize;
+        let nbr_leftover_elements = size_highest_level % self.group_size as usize;
+
+        let mut to_add = vec![];
+        for _ in 0..nbr_new_groups {
+            let mut first_key = None;
+            let mut values = RoaringBitmap::new();
+            for _ in 0..self.group_size {
+                let (key_bytes, value_i) = groups_iter.next().unwrap()?;
+                let key_i = FacetGroupKeyCodec::<BytesRefCodec>::bytes_decode(key_bytes)
+                    .map_err(heed::Error::Encoding)?;
+
+                if first_key.is_none() {
+                    first_key = Some(key_i);
+                }
+                values |= value_i.bitmap;
+            }
+            let key = FacetGroupKey {
+                field_id: self.field_id,
+                level: highest_level + 1,
+                left_bound: first_key.unwrap().left_bound,
+            };
+            let value = FacetGroupValue { size: self.group_size, bitmap: values };
+            to_add.push((key.into_owned(), value));
+        }
+        // now we add the rest of the level, in case its size is > group_size * min_level_size
+        // this can indeed happen if the min_level_size parameter changes between two calls to `insert`
+        if nbr_leftover_elements > 0 {
+            let mut first_key = None;
+            let mut values = RoaringBitmap::new();
+            for _ in 0..nbr_leftover_elements {
+                let (key_bytes, value_i) = groups_iter.next().unwrap()?;
+                let key_i = FacetGroupKeyCodec::<BytesRefCodec>::bytes_decode(key_bytes)
+                    .map_err(heed::Error::Encoding)?;
+
+                if first_key.is_none() {
+                    first_key = Some(key_i);
+                }
+                values |= value_i.bitmap;
+            }
+            let key = FacetGroupKey {
+                field_id: self.field_id,
+                level: highest_level + 1,
+                left_bound: first_key.unwrap().left_bound,
+            };
+            // Note: nbr_leftover_elements can be casted to a u8 since it is bounded by `max_group_size`
+            // when it is created above.
+            let value = FacetGroupValue { size: nbr_leftover_elements as u8, bitmap: values };
+            to_add.push((key.into_owned(), value));
+        }
+
+        drop(groups_iter);
+        for (key, value) in to_add {
+            self.db.put(txn, &key.as_ref(), &value)?;
+        }
+        Ok(())
+    }
+}
+
+#[derive(Debug)]
+pub struct FacetFieldIdChange {
+    pub facet_value: Box<[u8]>,
+    pub operation: FacetFieldIdOperation,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum FacetFieldIdOperation {
+    /// The docids have been modified for an existing facet value
+    ///
+    /// The modification must be propagated to upper levels, without changing the structure of the tree
+    InPlace,
+    /// A new value has been inserted
+    ///
+    /// The modification must be propagated to upper levels, splitting nodes and adding new levels as necessary.
+    Insert,
+    /// An existing value has been deleted
+    ///
+    /// The modification must be propagated to upper levels, merging nodes and removing levels as necessary.
+    Remove,
+}