diff --git a/Cargo.lock b/Cargo.lock
index 06bd9c234..335445956 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3598,6 +3598,7 @@ dependencies = [
  "smartstring",
  "tempfile",
  "thiserror",
+ "thread_local",
  "tiktoken-rs",
  "time",
  "tokenizers",
@@ -5332,9 +5333,9 @@ dependencies = [
 
 [[package]]
 name = "thread_local"
-version = "1.1.7"
+version = "1.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3fdd6f064ccff2d6567adcb3873ca630700f00b5ad3f060c25b5dcfd9a4ce152"
+checksum = "8b9ef9bad013ada3808854ceac7b46812a6465ba368859a37e2100283d2d719c"
 dependencies = [
  "cfg-if",
  "once_cell",
diff --git a/milli/Cargo.toml b/milli/Cargo.toml
index bae3dd64b..72f3daa4e 100644
--- a/milli/Cargo.toml
+++ b/milli/Cargo.toml
@@ -89,6 +89,7 @@ ureq = { version = "2.10.0", features = ["json"] }
 url = "2.5.2"
 rayon-par-bridge = "0.1.0"
 hashbrown = "0.14.5"
+thread_local = "1.1.8"
 
 [dev-dependencies]
 mimalloc = { version = "0.1.43", default-features = false }
diff --git a/milli/src/update/new/extract/faceted/extract_facets.rs b/milli/src/update/new/extract/faceted/extract_facets.rs
index f4ad50bfe..8e8b71676 100644
--- a/milli/src/update/new/extract/faceted/extract_facets.rs
+++ b/milli/src/update/new/extract/faceted/extract_facets.rs
@@ -1,3 +1,4 @@
+use std::cell::RefCell;
 use std::collections::HashSet;
 use std::fmt::Debug;
 use std::fs::File;
@@ -7,6 +8,7 @@ use grenad::{MergeFunction, Merger};
 use heed::RoTxn;
 use rayon::iter::{IntoParallelIterator, ParallelBridge, ParallelIterator};
 use serde_json::Value;
+use thread_local::ThreadLocal;
 
 use super::super::cache::CboCachedSorter;
 use super::facet_document::extract_document_facets;
@@ -216,24 +218,28 @@ impl DocidsExtractor for FacetedDocidsExtractor {
             let span =
                 tracing::trace_span!(target: "indexing::documents::extract", "docids_extraction");
             let _entered = span.enter();
+            let local = ThreadLocal::new();
             document_changes.into_par_iter().try_arc_for_each_try_init(
                 || {
-                    let rtxn = index.read_txn().map_err(Error::from)?;
-                    let cache = caches.push(CboCachedSorter::new(
-                        // TODO use a better value
-                        100.try_into().unwrap(),
-                        create_sorter(
-                            grenad::SortAlgorithm::Stable,
-                            MergeDeladdCboRoaringBitmaps,
-                            indexer.chunk_compression_type,
-                            indexer.chunk_compression_level,
-                            indexer.max_nb_chunks,
-                            max_memory,
-                        ),
-                    ));
-                    Ok((rtxn, fields_ids_map.clone(), Vec::new(), cache))
+                    local.get_or_try(|| {
+                        let rtxn = index.read_txn().map_err(Error::from)?;
+                        let cache = caches.push(CboCachedSorter::new(
+                            /// TODO use a better value
+                            100.try_into().unwrap(),
+                            create_sorter(
+                                grenad::SortAlgorithm::Stable,
+                                MergeDeladdCboRoaringBitmaps,
+                                indexer.chunk_compression_type,
+                                indexer.chunk_compression_level,
+                                indexer.max_nb_chunks,
+                                max_memory,
+                            ),
+                        ));
+                        Ok((rtxn, RefCell::new((fields_ids_map.clone(), Vec::new(), cache))))
+                    })
                 },
-                |(rtxn, fields_ids_map, buffer, cached_sorter), document_change| {
+                |(rtxn, rc), document_change| {
+                    let (fields_ids_map, buffer, cached_sorter) = &mut *rc.borrow_mut();
                     Self::extract_document_change(
                         rtxn,
                         index,
diff --git a/milli/src/update/new/extract/searchable/extract_word_docids.rs b/milli/src/update/new/extract/searchable/extract_word_docids.rs
index 702b8f4e9..df8409618 100644
--- a/milli/src/update/new/extract/searchable/extract_word_docids.rs
+++ b/milli/src/update/new/extract/searchable/extract_word_docids.rs
@@ -1,3 +1,4 @@
+use std::cell::RefCell;
 use std::collections::HashMap;
 use std::fs::File;
 use std::num::NonZero;
@@ -6,6 +7,7 @@ use std::sync::Arc;
 use grenad::{Merger, MergerBuilder};
 use heed::RoTxn;
 use rayon::iter::IntoParallelIterator;
+use thread_local::ThreadLocal;
 
 use super::tokenize_document::{tokenizer_builder, DocumentTokenizer};
 use super::SearchableExtractor;
@@ -347,18 +349,23 @@ impl WordDocidsExtractors {
             let span =
                 tracing::trace_span!(target: "indexing::documents::extract", "docids_extraction");
             let _entered = span.enter();
+            let local = ThreadLocal::new();
             document_changes.into_par_iter().try_arc_for_each_try_init(
                 || {
-                    let rtxn = index.read_txn().map_err(Error::from)?;
-                    let cache = caches.push(WordDocidsCachedSorters::new(
-                        indexer,
-                        max_memory,
-                        // TODO use a better value
-                        200_000.try_into().unwrap(),
-                    ));
-                    Ok((rtxn, &document_tokenizer, fields_ids_map.clone(), cache))
+                    local.get_or_try(|| {
+                        let rtxn = index.read_txn().map_err(Error::from)?;
+                        let fields_ids_map = fields_ids_map.clone();
+                        let cache = caches.push(WordDocidsCachedSorters::new(
+                            indexer,
+                            max_memory,
+                            // TODO use a better value
+                            200_000.try_into().unwrap(),
+                        ));
+                        Ok((rtxn, &document_tokenizer, RefCell::new((fields_ids_map, cache))))
+                    })
                 },
-                |(rtxn, document_tokenizer, fields_ids_map, cached_sorter), document_change| {
+                |(rtxn, document_tokenizer, rc), document_change| {
+                    let (fields_ids_map, cached_sorter) = &mut *rc.borrow_mut();
                     Self::extract_document_change(
                         rtxn,
                         index,
@@ -377,7 +384,9 @@ impl WordDocidsExtractors {
                 tracing::trace_span!(target: "indexing::documents::extract", "merger_building");
             let _entered = span.enter();
             let mut builder = WordDocidsMergerBuilders::new();
+            let mut count = 0;
             for cache in caches.into_iter() {
+                count += 1;
                 builder.add_sorters(cache)?;
             }
 
diff --git a/milli/src/update/new/extract/searchable/mod.rs b/milli/src/update/new/extract/searchable/mod.rs
index ba1d53f54..272bff4d3 100644
--- a/milli/src/update/new/extract/searchable/mod.rs
+++ b/milli/src/update/new/extract/searchable/mod.rs
@@ -2,6 +2,7 @@ mod extract_word_docids;
 mod extract_word_pair_proximity_docids;
 mod tokenize_document;
 
+use std::cell::RefCell;
 use std::fs::File;
 use std::sync::Arc;
 
@@ -10,6 +11,7 @@ pub use extract_word_pair_proximity_docids::WordPairProximityDocidsExtractor;
 use grenad::Merger;
 use heed::RoTxn;
 use rayon::iter::{IntoParallelIterator, ParallelBridge, ParallelIterator};
+use thread_local::ThreadLocal;
 use tokenize_document::{tokenizer_builder, DocumentTokenizer};
 
 use super::cache::CboCachedSorter;
@@ -64,24 +66,32 @@ pub trait SearchableExtractor {
             let span =
                 tracing::trace_span!(target: "indexing::documents::extract", "docids_extraction");
             let _entered = span.enter();
+            let local = ThreadLocal::new();
             document_changes.into_par_iter().try_arc_for_each_try_init(
                 || {
-                    let rtxn = index.read_txn().map_err(Error::from)?;
-                    let cache = caches.push(CboCachedSorter::new(
-                        // TODO use a better value
-                        1_000_000.try_into().unwrap(),
-                        create_sorter(
-                            grenad::SortAlgorithm::Stable,
-                            MergeDeladdCboRoaringBitmaps,
-                            indexer.chunk_compression_type,
-                            indexer.chunk_compression_level,
-                            indexer.max_nb_chunks,
-                            max_memory,
-                        ),
-                    ));
-                    Ok((rtxn, &document_tokenizer, fields_ids_map.clone(), cache))
+                    local.get_or_try(|| {
+                        let rtxn = index.read_txn().map_err(Error::from)?;
+                        let cache = caches.push(CboCachedSorter::new(
+                            /// TODO use a better value
+                            1_000_000.try_into().unwrap(),
+                            create_sorter(
+                                grenad::SortAlgorithm::Stable,
+                                MergeDeladdCboRoaringBitmaps,
+                                indexer.chunk_compression_type,
+                                indexer.chunk_compression_level,
+                                indexer.max_nb_chunks,
+                                max_memory,
+                            ),
+                        ));
+                        Ok((
+                            rtxn,
+                            &document_tokenizer,
+                            RefCell::new((fields_ids_map.clone(), cache)),
+                        ))
+                    })
                 },
-                |(rtxn, document_tokenizer, fields_ids_map, cached_sorter), document_change| {
+                |(rtxn, document_tokenizer, rc), document_change| {
+                    let (fields_ids_map, cached_sorter) = &mut *rc.borrow_mut();
                     Self::extract_document_change(
                         rtxn,
                         index,