diff --git a/milli/src/update/index_documents/extract/extract_facet_number_docids.rs b/milli/src/update/index_documents/extract/extract_facet_number_docids.rs
index b5550a765..6c6243663 100644
--- a/milli/src/update/index_documents/extract/extract_facet_number_docids.rs
+++ b/milli/src/update/index_documents/extract/extract_facet_number_docids.rs
@@ -1,5 +1,6 @@
 use std::fs::File;
 use std::io::{self, BufReader};
+use std::num::NonZeroUsize;
 
 use heed::{BytesDecode, BytesEncode};
 
@@ -9,8 +10,10 @@ use super::helpers::{
 use crate::heed_codec::facet::{
     FacetGroupKey, FacetGroupKeyCodec, FieldDocIdFacetF64Codec, OrderedF64Codec,
 };
-use crate::update::del_add::{KvReaderDelAdd, KvWriterDelAdd};
+use crate::update::del_add::{DelAdd, KvReaderDelAdd};
+use crate::update::index_documents::cache::SorterCacheDelAddCboRoaringBitmap;
 use crate::update::settings::InnerIndexSettingsDiff;
+use crate::update::MergeFn;
 use crate::Result;
 
 /// Extracts the facet number and the documents ids where this facet number appear.
@@ -23,10 +26,9 @@ pub fn extract_facet_number_docids<R: io::Read + io::Seek>(
     indexer: GrenadParameters,
     _settings_diff: &InnerIndexSettingsDiff,
 ) -> Result<grenad::Reader<BufReader<File>>> {
-    let mut conn = super::REDIS_CLIENT.get_connection().unwrap();
     let max_memory = indexer.max_memory_by_thread();
 
-    let mut facet_number_docids_sorter = create_sorter(
+    let facet_number_docids_sorter = create_sorter(
         grenad::SortAlgorithm::Unstable,
         merge_deladd_cbo_roaring_bitmaps,
         indexer.chunk_compression_type,
@@ -34,8 +36,13 @@ pub fn extract_facet_number_docids<R: io::Read + io::Seek>(
         indexer.max_nb_chunks,
         max_memory,
     );
+    let mut cached_facet_number_docids_sorter =
+        SorterCacheDelAddCboRoaringBitmap::<20, MergeFn>::new(
+            NonZeroUsize::new(20).unwrap(),
+            facet_number_docids_sorter,
+            super::REDIS_CLIENT.get_connection().unwrap(),
+        );
 
-    let mut buffer = Vec::new();
     let mut cursor = fid_docid_facet_number.into_cursor()?;
     while let Some((key_bytes, deladd_obkv_bytes)) = cursor.move_on_next()? {
         let (field_id, document_id, number) =
@@ -43,17 +50,17 @@ pub fn extract_facet_number_docids<R: io::Read + io::Seek>(
 
         let key = FacetGroupKey { field_id, level: 0, left_bound: number };
         let key_bytes = FacetGroupKeyCodec::<OrderedF64Codec>::bytes_encode(&key).unwrap();
-
-        buffer.clear();
-        let mut obkv = KvWriterDelAdd::new(&mut buffer);
         for (deladd_key, _) in KvReaderDelAdd::new(deladd_obkv_bytes).iter() {
-            obkv.insert(deladd_key, document_id.to_ne_bytes())?;
+            match deladd_key {
+                DelAdd::Deletion => {
+                    cached_facet_number_docids_sorter.insert_del_u32(&key_bytes, document_id)?
+                }
+                DelAdd::Addition => {
+                    cached_facet_number_docids_sorter.insert_add_u32(&key_bytes, document_id)?
+                }
+            }
         }
-        obkv.finish()?;
-
-        redis::cmd("INCR").arg(key_bytes.as_ref()).query::<usize>(&mut conn).unwrap();
-        facet_number_docids_sorter.insert(key_bytes, &buffer)?;
     }
 
-    sorter_into_reader(facet_number_docids_sorter, indexer)
+    sorter_into_reader(cached_facet_number_docids_sorter.into_sorter()?, indexer)
 }