diff --git a/Cargo.toml b/Cargo.toml
index 77fede634..c1526a286 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -53,10 +53,11 @@ lru = "0.7.5"
 fastdivide = "0.4.0"
 itertools = "0.10.3"
 measure_time = "0.8.2"
-ciborium = { version = "0.2", optional = true}
 async-trait = "0.1.53"
 arc-swap = "1.5.0"
 
+sstable = { version="0.1", path="./sstable", package ="tantivy-sstable", optional = true }
+stacker = { version="0.1", path="./stacker", package ="tantivy-stacker" }
 tantivy-query-grammar = { version= "0.19.0", path="./query-grammar" }
 tantivy-bitpacker = 		{ version= "0.3", path="./bitpacker" }
 common = 								{ version= "0.4", path = "./common/", package = "tantivy-common" }
@@ -104,10 +105,10 @@ zstd-compression = ["zstd"]
 failpoints = ["fail/failpoints"]
 unstable = [] # useful for benches.
 
-quickwit = ["ciborium"]
+quickwit = ["sstable"]
 
 [workspace]
-members = ["query-grammar", "bitpacker", "common", "fastfield_codecs", "ownedbytes"]
+members = ["query-grammar", "bitpacker", "common", "fastfield_codecs", "ownedbytes", "stacker", "sstable"]
 
 # Following the "fail" crate best practises, we isolate
 # tests that define specific behavior in fail check points
diff --git a/src/postings/indexing_context.rs b/src/postings/indexing_context.rs
index 9fc8a922f..074361d86 100644
--- a/src/postings/indexing_context.rs
+++ b/src/postings/indexing_context.rs
@@ -1,11 +1,11 @@
-use crate::postings::stacker::{MemoryArena, TermHashMap};
+use stacker::{ArenaHashMap, MemoryArena};
 
 /// IndexingContext contains all of the transient memory arenas
 /// required for building the inverted index.
 pub(crate) struct IndexingContext {
     /// The term index is an adhoc hashmap,
     /// itself backed by a dedicated memory arena.
-    pub term_index: TermHashMap,
+    pub term_index: ArenaHashMap,
     /// Arena is a memory arena that stores posting lists / term frequencies / positions.
     pub arena: MemoryArena,
 }
@@ -13,9 +13,9 @@ pub(crate) struct IndexingContext {
 impl IndexingContext {
     /// Create a new IndexingContext given the size of the term hash map.
     pub(crate) fn new(table_size: usize) -> IndexingContext {
-        let term_index = TermHashMap::new(table_size);
+        let term_index = ArenaHashMap::new(table_size);
         IndexingContext {
-            arena: MemoryArena::new(),
+            arena: MemoryArena::default(),
             term_index,
         }
     }
diff --git a/src/postings/json_postings_writer.rs b/src/postings/json_postings_writer.rs
index 34a5092e9..2e29aa0a0 100644
--- a/src/postings/json_postings_writer.rs
+++ b/src/postings/json_postings_writer.rs
@@ -1,10 +1,11 @@
 use std::io;
 
+use stacker::Addr;
+
 use crate::fastfield::MultiValuedFastFieldWriter;
 use crate::indexer::doc_id_mapping::DocIdMapping;
 use crate::postings::postings_writer::SpecializedPostingsWriter;
 use crate::postings::recorder::{BufferLender, DocIdRecorder, Recorder};
-use crate::postings::stacker::Addr;
 use crate::postings::{
     FieldSerializer, IndexingContext, IndexingPosition, PostingsWriter, UnorderedTermId,
 };
diff --git a/src/postings/mod.rs b/src/postings/mod.rs
index fe42cbff6..df10e4e40 100644
--- a/src/postings/mod.rs
+++ b/src/postings/mod.rs
@@ -15,9 +15,10 @@ mod recorder;
 mod segment_postings;
 mod serializer;
 mod skip;
-mod stacker;
 mod term_info;
 
+pub(crate) use stacker::compute_table_size;
+
 pub use self::block_segment_postings::BlockSegmentPostings;
 pub(crate) use self::indexing_context::IndexingContext;
 pub(crate) use self::per_field_postings_writer::PerFieldPostingsWriter;
@@ -26,10 +27,9 @@ pub(crate) use self::postings_writer::{serialize_postings, IndexingPosition, Pos
 pub use self::segment_postings::SegmentPostings;
 pub use self::serializer::{FieldSerializer, InvertedIndexSerializer};
 pub(crate) use self::skip::{BlockInfo, SkipReader};
-pub(crate) use self::stacker::compute_table_size;
 pub use self::term_info::TermInfo;
 
-pub(crate) type UnorderedTermId = u64;
+pub(crate) type UnorderedTermId = stacker::UnorderedId;
 
 #[allow(clippy::enum_variant_names)]
 #[derive(Debug, PartialEq, Clone, Copy, Eq)]
diff --git a/src/postings/postings_writer.rs b/src/postings/postings_writer.rs
index 656a05bc3..19c127475 100644
--- a/src/postings/postings_writer.rs
+++ b/src/postings/postings_writer.rs
@@ -4,8 +4,8 @@ use std::marker::PhantomData;
 use std::ops::Range;
 
 use rustc_hash::FxHashMap;
+use stacker::Addr;
 
-use super::stacker::Addr;
 use crate::fastfield::MultiValuedFastFieldWriter;
 use crate::fieldnorm::FieldNormReaders;
 use crate::indexer::doc_id_mapping::DocIdMapping;
@@ -59,7 +59,11 @@ pub(crate) fn serialize_postings(
 ) -> crate::Result<HashMap<Field, FxHashMap<UnorderedTermId, TermOrdinal>>> {
     let mut term_offsets: Vec<(Term<&[u8]>, Addr, UnorderedTermId)> =
         Vec::with_capacity(ctx.term_index.len());
-    term_offsets.extend(ctx.term_index.iter());
+    term_offsets.extend(
+        ctx.term_index
+            .iter()
+            .map(|(bytes, addr, unordered_id)| (Term::wrap(bytes), addr, unordered_id)),
+    );
     term_offsets.sort_unstable_by_key(|(k, _, _)| k.clone());
     let mut unordered_term_mappings: HashMap<Field, FxHashMap<UnorderedTermId, TermOrdinal>> =
         HashMap::new();
diff --git a/src/postings/recorder.rs b/src/postings/recorder.rs
index e66993e09..35788787e 100644
--- a/src/postings/recorder.rs
+++ b/src/postings/recorder.rs
@@ -1,6 +1,6 @@
 use common::read_u32_vint;
+use stacker::{ExpUnrolledLinkedList, MemoryArena};
 
-use super::stacker::{ExpUnrolledLinkedList, MemoryArena};
 use crate::indexer::doc_id_mapping::DocIdMapping;
 use crate::postings::FieldSerializer;
 use crate::DocId;
@@ -91,7 +91,7 @@ pub struct DocIdRecorder {
 impl Default for DocIdRecorder {
     fn default() -> Self {
         DocIdRecorder {
-            stack: ExpUnrolledLinkedList::new(),
+            stack: ExpUnrolledLinkedList::default(),
             current_doc: u32::MAX,
         }
     }
@@ -144,7 +144,7 @@ impl Recorder for DocIdRecorder {
 }
 
 /// Recorder encoding document ids, and term frequencies
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Default)]
 pub struct TermFrequencyRecorder {
     stack: ExpUnrolledLinkedList,
     current_doc: DocId,
@@ -152,17 +152,6 @@ pub struct TermFrequencyRecorder {
     term_doc_freq: u32,
 }
 
-impl Default for TermFrequencyRecorder {
-    fn default() -> Self {
-        TermFrequencyRecorder {
-            stack: ExpUnrolledLinkedList::new(),
-            current_doc: 0,
-            current_tf: 0u32,
-            term_doc_freq: 0u32,
-        }
-    }
-}
-
 impl Recorder for TermFrequencyRecorder {
     fn current_doc(&self) -> DocId {
         self.current_doc
@@ -229,7 +218,7 @@ pub struct TfAndPositionRecorder {
 impl Default for TfAndPositionRecorder {
     fn default() -> Self {
         TfAndPositionRecorder {
-            stack: ExpUnrolledLinkedList::new(),
+            stack: ExpUnrolledLinkedList::default(),
             current_doc: u32::MAX,
             term_doc_freq: 0u32,
         }
diff --git a/src/postings/stacker/mod.rs b/src/postings/stacker/mod.rs
deleted file mode 100644
index 19fff9216..000000000
--- a/src/postings/stacker/mod.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-mod expull;
-mod memory_arena;
-mod term_hashmap;
-
-pub(crate) use self::expull::ExpUnrolledLinkedList;
-pub(crate) use self::memory_arena::{Addr, MemoryArena};
-pub(crate) use self::term_hashmap::{compute_table_size, TermHashMap};
diff --git a/src/termdict/sstable_termdict/mod.rs b/src/termdict/sstable_termdict/mod.rs
index 5b1174686..729fd73da 100644
--- a/src/termdict/sstable_termdict/mod.rs
+++ b/src/termdict/sstable_termdict/mod.rs
@@ -1,17 +1,16 @@
 use std::io;
 
 mod merger;
-mod sstable;
 mod streamer;
 mod termdict;
 
 use std::iter::ExactSizeIterator;
 
 use common::VInt;
+use sstable::value::{ValueReader, ValueWriter};
+use sstable::{BlockReader, SSTable};
 
 pub use self::merger::TermMerger;
-use self::sstable::value::{ValueReader, ValueWriter};
-use self::sstable::{BlockReader, SSTable};
 pub use self::streamer::{TermStreamer, TermStreamerBuilder};
 pub use self::termdict::{TermDictionary, TermDictionaryBuilder};
 use crate::postings::TermInfo;
diff --git a/src/termdict/sstable_termdict/streamer.rs b/src/termdict/sstable_termdict/streamer.rs
index ef388dc17..8289862ec 100644
--- a/src/termdict/sstable_termdict/streamer.rs
+++ b/src/termdict/sstable_termdict/streamer.rs
@@ -87,7 +87,7 @@ where
 {
     automaton: A,
     states: Vec<A::State>,
-    delta_reader: super::sstable::DeltaReader<'a, TermInfoReader>,
+    delta_reader: sstable::DeltaReader<'a, TermInfoReader>,
     key: Vec<u8>,
     term_ord: Option<TermOrdinal>,
     lower_bound: Bound<Vec<u8>>,
diff --git a/src/termdict/sstable_termdict/termdict.rs b/src/termdict/sstable_termdict/termdict.rs
index 7c4f8ae5f..c618d7ecf 100644
--- a/src/termdict/sstable_termdict/termdict.rs
+++ b/src/termdict/sstable_termdict/termdict.rs
@@ -3,15 +3,12 @@ use std::sync::Arc;
 
 use common::BinarySerializable;
 use once_cell::sync::Lazy;
+use sstable::{BlockAddr, DeltaReader, Reader, SSTable, SSTableIndex, Writer};
 use tantivy_fst::automaton::AlwaysMatch;
 use tantivy_fst::Automaton;
 
 use crate::directory::{FileSlice, OwnedBytes};
 use crate::postings::TermInfo;
-use crate::termdict::sstable_termdict::sstable::sstable_index::BlockAddr;
-use crate::termdict::sstable_termdict::sstable::{
-    DeltaReader, Reader, SSTable, SSTableIndex, Writer,
-};
 use crate::termdict::sstable_termdict::{
     TermInfoReader, TermInfoWriter, TermSSTable, TermStreamer, TermStreamerBuilder,
 };
@@ -132,7 +129,8 @@ impl TermDictionary {
         let num_terms = u64::deserialize(&mut footer_len_bytes)?;
         let (sstable_slice, index_slice) = main_slice.split(index_offset as usize);
         let sstable_index_bytes = index_slice.read_bytes()?;
-        let sstable_index = SSTableIndex::load(sstable_index_bytes.as_slice())?;
+        let sstable_index = SSTableIndex::load(sstable_index_bytes.as_slice())
+            .map_err(|_| crate::error::DataCorruption::comment_only("SSTable corruption"))?;
         Ok(TermDictionary {
             sstable_slice,
             sstable_index,
diff --git a/sstable/Cargo.toml b/sstable/Cargo.toml
new file mode 100644
index 000000000..1f50efa7d
--- /dev/null
+++ b/sstable/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "tantivy-sstable"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+common = {path="../common", package="tantivy-common"}
+ciborium = "0.2"
+byteorder = "1"
+serde = "1"
+
+[dev-dependencies]
+proptest = "1"
diff --git a/src/termdict/sstable_termdict/sstable/block_reader.rs b/sstable/src/block_reader.rs
similarity index 100%
rename from src/termdict/sstable_termdict/sstable/block_reader.rs
rename to sstable/src/block_reader.rs
diff --git a/src/termdict/sstable_termdict/sstable/delta.rs b/sstable/src/delta.rs
similarity index 100%
rename from src/termdict/sstable_termdict/sstable/delta.rs
rename to sstable/src/delta.rs
diff --git a/src/termdict/sstable_termdict/sstable/mod.rs b/sstable/src/lib.rs
similarity index 97%
rename from src/termdict/sstable_termdict/sstable/mod.rs
rename to sstable/src/lib.rs
index 0afef761c..59288f165 100644
--- a/src/termdict/sstable_termdict/sstable/mod.rs
+++ b/sstable/src/lib.rs
@@ -7,21 +7,19 @@ mod delta;
 pub mod merge;
 pub mod value;
 
-pub(crate) mod sstable_index;
-
-pub(crate) use self::sstable_index::{SSTableIndex, SSTableIndexBuilder};
+mod sstable_index;
+pub use sstable_index::{BlockAddr, SSTableIndex, SSTableIndexBuilder};
 pub(crate) mod vint;
 
 mod block_reader;
 pub use self::block_reader::BlockReader;
-pub use self::delta::DeltaReader;
-use self::delta::DeltaWriter;
+pub use self::delta::{DeltaReader, DeltaWriter};
 pub use self::merge::VoidMerge;
 use self::value::{U64MonotonicReader, U64MonotonicWriter, ValueReader, ValueWriter};
 
 const DEFAULT_KEY_CAPACITY: usize = 50;
 
-pub(crate) fn common_prefix_len(left: &[u8], right: &[u8]) -> usize {
+fn common_prefix_len(left: &[u8], right: &[u8]) -> usize {
     left.iter()
         .cloned()
         .zip(right.iter().cloned())
@@ -29,6 +27,9 @@ pub(crate) fn common_prefix_len(left: &[u8], right: &[u8]) -> usize {
         .count()
 }
 
+#[derive(Debug, Copy, Clone)]
+pub struct SSTableDataCorruption;
+
 pub trait SSTable: Sized {
     type Value;
     type Reader: ValueReader<Value = Self::Value>;
diff --git a/src/termdict/sstable_termdict/sstable/merge/heap_merge.rs b/sstable/src/merge/heap_merge.rs
similarity index 96%
rename from src/termdict/sstable_termdict/sstable/merge/heap_merge.rs
rename to sstable/src/merge/heap_merge.rs
index 50af21962..9e852918d 100644
--- a/src/termdict/sstable_termdict/sstable/merge/heap_merge.rs
+++ b/sstable/src/merge/heap_merge.rs
@@ -4,7 +4,7 @@ use std::collections::BinaryHeap;
 use std::io;
 
 use super::{SingleValueMerger, ValueMerger};
-use crate::termdict::sstable_termdict::sstable::{Reader, SSTable, Writer};
+use crate::{Reader, SSTable, Writer};
 
 struct HeapItem<B: AsRef<[u8]>>(B);
 
diff --git a/src/termdict/sstable_termdict/sstable/merge/mod.rs b/sstable/src/merge/mod.rs
similarity index 100%
rename from src/termdict/sstable_termdict/sstable/merge/mod.rs
rename to sstable/src/merge/mod.rs
diff --git a/src/termdict/sstable_termdict/sstable/sstable_index.rs b/sstable/src/sstable_index.rs
similarity index 92%
rename from src/termdict/sstable_termdict/sstable/sstable_index.rs
rename to sstable/src/sstable_index.rs
index 14f795178..c7e132e89 100644
--- a/src/termdict/sstable_termdict/sstable/sstable_index.rs
+++ b/sstable/src/sstable_index.rs
@@ -3,8 +3,7 @@ use std::ops::Range;
 
 use serde::{Deserialize, Serialize};
 
-use crate::error::DataCorruption;
-use crate::termdict::sstable_termdict::sstable::common_prefix_len;
+use crate::{common_prefix_len, SSTableDataCorruption};
 
 #[derive(Default, Debug, Serialize, Deserialize)]
 pub struct SSTableIndex {
@@ -12,9 +11,8 @@ pub struct SSTableIndex {
 }
 
 impl SSTableIndex {
-    pub(crate) fn load(data: &[u8]) -> Result<SSTableIndex, DataCorruption> {
-        ciborium::de::from_reader(data)
-            .map_err(|_| DataCorruption::comment_only("SSTable index is corrupted"))
+    pub fn load(data: &[u8]) -> Result<SSTableIndex, SSTableDataCorruption> {
+        ciborium::de::from_reader(data).map_err(|_| SSTableDataCorruption)
     }
 
     pub fn search(&self, key: &[u8]) -> Option<BlockAddr> {
@@ -94,6 +92,7 @@ impl SSTableIndexBuilder {
 #[cfg(test)]
 mod tests {
     use super::{BlockAddr, SSTableIndex, SSTableIndexBuilder};
+    use crate::SSTableDataCorruption;
 
     #[test]
     fn test_sstable_index() {
@@ -125,10 +124,7 @@ mod tests {
         sstable_builder.serialize(&mut buffer).unwrap();
         buffer[1] = 9u8;
         let data_corruption_err = SSTableIndex::load(&buffer[..]).err().unwrap();
-        assert_eq!(
-            format!("{data_corruption_err:?}"),
-            "Data corruption: SSTable index is corrupted."
-        );
+        assert!(matches!(data_corruption_err, SSTableDataCorruption));
     }
 
     #[track_caller]
diff --git a/src/termdict/sstable_termdict/sstable/value.rs b/sstable/src/value.rs
similarity index 100%
rename from src/termdict/sstable_termdict/sstable/value.rs
rename to sstable/src/value.rs
diff --git a/src/termdict/sstable_termdict/sstable/vint.rs b/sstable/src/vint.rs
similarity index 100%
rename from src/termdict/sstable_termdict/sstable/vint.rs
rename to sstable/src/vint.rs
diff --git a/stacker/Cargo.toml b/stacker/Cargo.toml
new file mode 100644
index 000000000..f683ff5ec
--- /dev/null
+++ b/stacker/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "tantivy-stacker"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+murmurhash32 = "0.2"
+byteorder = "1"
+common = { version = "0.4", path = "../common/", package = "tantivy-common" }
diff --git a/src/postings/stacker/term_hashmap.rs b/stacker/src/arena_hashmap.rs
similarity index 86%
rename from src/postings/stacker/term_hashmap.rs
rename to stacker/src/arena_hashmap.rs
index 19c29b7ca..5bd8eaf22 100644
--- a/src/postings/stacker/term_hashmap.rs
+++ b/stacker/src/arena_hashmap.rs
@@ -4,14 +4,13 @@ use byteorder::{ByteOrder, NativeEndian};
 use murmurhash32::murmurhash2;
 
 use super::{Addr, MemoryArena};
-use crate::postings::stacker::memory_arena::store;
-use crate::postings::UnorderedTermId;
-use crate::Term;
+use crate::memory_arena::store;
+use crate::UnorderedId;
 
 /// Returns the actual memory size in bytes
 /// required to create a table with a given capacity.
 /// required to create a table of size
-pub(crate) fn compute_table_size(capacity: usize) -> usize {
+pub fn compute_table_size(capacity: usize) -> usize {
     capacity * mem::size_of::<KeyValue>()
 }
 
@@ -22,7 +21,7 @@ pub(crate) fn compute_table_size(capacity: usize) -> usize {
 struct KeyValue {
     key_value_addr: Addr,
     hash: u32,
-    unordered_term_id: UnorderedTermId,
+    unordered_id: UnorderedId,
 }
 
 impl Default for KeyValue {
@@ -30,7 +29,7 @@ impl Default for KeyValue {
         KeyValue {
             key_value_addr: Addr::null_pointer(),
             hash: 0u32,
-            unordered_term_id: UnorderedTermId::default(),
+            unordered_id: UnorderedId::default(),
         }
     }
 }
@@ -41,15 +40,16 @@ impl KeyValue {
     }
 }
 
-/// Customized `HashMap` with string keys
+/// Customized `HashMap` with `&[u8]` keys
 ///
-/// This `HashMap` takes String as keys. Keys are
-/// stored in a user defined memory arena.
+/// Its main particularity is that rather than storing its
+/// keys in the heap, keys are stored in a memory arena
+/// inline with the values.
 ///
 /// The quirky API has the benefit of avoiding
 /// the computation of the hash of the key twice,
 /// or copying the key as long as there is no insert.
-pub struct TermHashMap {
+pub struct ArenaHashMap {
     table: Box<[KeyValue]>,
     memory_arena: MemoryArena,
     mask: usize,
@@ -64,6 +64,7 @@ struct QuadraticProbing {
 }
 
 impl QuadraticProbing {
+    #[inline]
     fn compute(hash: usize, mask: usize) -> QuadraticProbing {
         QuadraticProbing { hash, i: 0, mask }
     }
@@ -76,18 +77,18 @@ impl QuadraticProbing {
 }
 
 pub struct Iter<'a> {
-    hashmap: &'a TermHashMap,
+    hashmap: &'a ArenaHashMap,
     inner: slice::Iter<'a, usize>,
 }
 
 impl<'a> Iterator for Iter<'a> {
-    type Item = (Term<&'a [u8]>, Addr, UnorderedTermId);
+    type Item = (&'a [u8], Addr, UnorderedId);
 
     fn next(&mut self) -> Option<Self::Item> {
         self.inner.next().cloned().map(move |bucket: usize| {
             let kv = self.hashmap.table[bucket];
             let (key, offset): (&'a [u8], Addr) = self.hashmap.get_key_value(kv.key_value_addr);
-            (Term::wrap(key), offset, kv.unordered_term_id)
+            (key, offset, kv.unordered_id)
         })
     }
 }
@@ -102,15 +103,15 @@ fn compute_previous_power_of_two(n: usize) -> usize {
     1 << msb
 }
 
-impl TermHashMap {
-    pub(crate) fn new(table_size: usize) -> TermHashMap {
+impl ArenaHashMap {
+    pub fn new(table_size: usize) -> ArenaHashMap {
         assert!(table_size > 0);
         let table_size_power_of_2 = compute_previous_power_of_two(table_size);
-        let memory_arena = MemoryArena::new();
+        let memory_arena = MemoryArena::default();
         let table: Vec<KeyValue> = iter::repeat(KeyValue::default())
             .take(table_size_power_of_2)
             .collect();
-        TermHashMap {
+        ArenaHashMap {
             table: table.into_boxed_slice(),
             memory_arena,
             mask: table_size_power_of_2 - 1,
@@ -119,18 +120,22 @@ impl TermHashMap {
         }
     }
 
+    #[inline]
     pub fn read<Item: Copy + 'static>(&self, addr: Addr) -> Item {
         self.memory_arena.read(addr)
     }
 
+    #[inline]
     fn probe(&self, hash: u32) -> QuadraticProbing {
         QuadraticProbing::compute(hash as usize, self.mask)
     }
 
+    #[inline]
     pub fn mem_usage(&self) -> usize {
         self.table.len() * mem::size_of::<KeyValue>()
     }
 
+    #[inline]
     fn is_saturated(&self) -> bool {
         self.table.len() < self.occupied.len() * 3
     }
@@ -153,22 +158,30 @@ impl TermHashMap {
         }
     }
 
-    fn set_bucket(&mut self, hash: u32, key_value_addr: Addr, bucket: usize) -> UnorderedTermId {
+    #[inline]
+    fn set_bucket(&mut self, hash: u32, key_value_addr: Addr, bucket: usize) -> UnorderedId {
         self.occupied.push(bucket);
-        let unordered_term_id = self.len as UnorderedTermId;
+        let unordered_id = self.len as UnorderedId;
         self.len += 1;
         self.table[bucket] = KeyValue {
             key_value_addr,
             hash,
-            unordered_term_id,
+            unordered_id,
         };
-        unordered_term_id
+        unordered_id
     }
 
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    #[inline]
     pub fn len(&self) -> usize {
         self.len
     }
 
+    #[inline]
     pub fn iter(&self) -> Iter<'_> {
         Iter {
             inner: self.occupied.iter(),
@@ -210,7 +223,7 @@ impl TermHashMap {
         &mut self,
         key: &[u8],
         mut updater: TMutator,
-    ) -> UnorderedTermId
+    ) -> UnorderedId
     where
         V: Copy + 'static,
         TMutator: FnMut(Option<V>) -> V,
@@ -241,7 +254,7 @@ impl TermHashMap {
                     let v = self.memory_arena.read(val_addr);
                     let new_v = updater(Some(v));
                     self.memory_arena.write_at(val_addr, new_v);
-                    return kv.unordered_term_id;
+                    return kv.unordered_id;
                 }
             }
         }
@@ -253,11 +266,11 @@ mod tests {
 
     use std::collections::HashMap;
 
-    use super::{compute_previous_power_of_two, TermHashMap};
+    use super::{compute_previous_power_of_two, ArenaHashMap};
 
     #[test]
     fn test_hash_map() {
-        let mut hash_map: TermHashMap = TermHashMap::new(1 << 18);
+        let mut hash_map: ArenaHashMap = ArenaHashMap::new(1 << 18);
         hash_map.mutate_or_create(b"abc", |opt_val: Option<u32>| {
             assert_eq!(opt_val, None);
             3u32
diff --git a/src/postings/stacker/expull.rs b/stacker/src/expull.rs
similarity index 93%
rename from src/postings/stacker/expull.rs
rename to stacker/src/expull.rs
index cbd66ceb8..7ebb59f50 100644
--- a/src/postings/stacker/expull.rs
+++ b/stacker/src/expull.rs
@@ -2,8 +2,8 @@ use std::mem;
 
 use common::serialize_vint_u32;
 
-use super::{Addr, MemoryArena};
-use crate::postings::stacker::memory_arena::{load, store};
+use crate::memory_arena::{load, store};
+use crate::{Addr, MemoryArena};
 
 const MAX_BLOCK_LEN: u32 = 1u32 << 15;
 const FIRST_BLOCK: usize = 16;
@@ -120,15 +120,17 @@ impl<'a> ExpUnrolledLinkedListWriter<'a> {
     }
 }
 
-impl ExpUnrolledLinkedList {
-    pub fn new() -> ExpUnrolledLinkedList {
+impl Default for ExpUnrolledLinkedList {
+    fn default() -> ExpUnrolledLinkedList {
         ExpUnrolledLinkedList {
             len: 0u32,
             tail: Addr::null_pointer(),
             inlined_data: [0u8; INLINED_BLOCK_LEN as usize],
         }
     }
+}
 
+impl ExpUnrolledLinkedList {
     #[inline]
     pub fn writer<'a>(&'a mut self, arena: &'a mut MemoryArena) -> ExpUnrolledLinkedListWriter<'a> {
         ExpUnrolledLinkedListWriter { eull: self, arena }
@@ -169,8 +171,8 @@ mod tests {
 
     #[test]
     fn test_eull() {
-        let mut arena = MemoryArena::new();
-        let mut stack = ExpUnrolledLinkedList::new();
+        let mut arena = MemoryArena::default();
+        let mut stack = ExpUnrolledLinkedList::default();
         stack.writer(&mut arena).extend_from_slice(&[1u8]);
         stack.writer(&mut arena).extend_from_slice(&[2u8]);
         stack.writer(&mut arena).extend_from_slice(&[3u8, 4u8]);
@@ -184,8 +186,8 @@ mod tests {
 
     #[test]
     fn test_eull_long() {
-        let mut arena = MemoryArena::new();
-        let mut eull = ExpUnrolledLinkedList::new();
+        let mut arena = MemoryArena::default();
+        let mut eull = ExpUnrolledLinkedList::default();
         let data: Vec<u32> = (0..100).collect();
         for &el in &data {
             eull.writer(&mut arena).write_u32_vint(el);
@@ -202,9 +204,9 @@ mod tests {
 
     #[test]
     fn test_eull_interlaced() {
-        let mut eull = MemoryArena::new();
-        let mut stack = ExpUnrolledLinkedList::new();
-        let mut stack2 = ExpUnrolledLinkedList::new();
+        let mut eull = MemoryArena::default();
+        let mut stack = ExpUnrolledLinkedList::default();
+        let mut stack2 = ExpUnrolledLinkedList::default();
 
         let mut vec1: Vec<u8> = vec![];
         let mut vec2: Vec<u8> = vec![];
@@ -306,9 +308,9 @@ mod bench {
     #[bench]
     fn bench_push_stack(bench: &mut Bencher) {
         bench.iter(|| {
-            let mut arena = MemoryArena::new();
+            let mut arena = MemoryArena::default();
             let mut stacks: Vec<ExpUnrolledLinkedList> =
-                iter::repeat_with(ExpUnrolledLinkedList::new)
+                iter::repeat_with(ExpUnrolledLinkedList::default)
                     .take(NUM_STACK)
                     .collect();
             for s in 0..NUM_STACK {
diff --git a/stacker/src/lib.rs b/stacker/src/lib.rs
new file mode 100644
index 000000000..add06359a
--- /dev/null
+++ b/stacker/src/lib.rs
@@ -0,0 +1,10 @@
+mod arena_hashmap;
+mod expull;
+mod memory_arena;
+
+pub use self::arena_hashmap::{compute_table_size, ArenaHashMap};
+pub use self::expull::ExpUnrolledLinkedList;
+pub use self::memory_arena::{Addr, MemoryArena};
+
+/// When adding an element in a `ArenaHashMap`, we get a unique id associated to the given key.
+pub type UnorderedId = u64;
diff --git a/src/postings/stacker/memory_arena.rs b/stacker/src/memory_arena.rs
similarity index 97%
rename from src/postings/stacker/memory_arena.rs
rename to stacker/src/memory_arena.rs
index 41ec95e53..2155d4a0f 100644
--- a/src/postings/stacker/memory_arena.rs
+++ b/stacker/src/memory_arena.rs
@@ -86,15 +86,16 @@ pub struct MemoryArena {
     pages: Vec<Page>,
 }
 
-impl MemoryArena {
-    /// Creates a new memory arena.
-    pub fn new() -> MemoryArena {
+impl Default for MemoryArena {
+    fn default() -> MemoryArena {
         let first_page = Page::new(0);
         MemoryArena {
             pages: vec![first_page],
         }
     }
+}
 
+impl MemoryArena {
     fn add_page(&mut self) -> &mut Page {
         let new_page_id = self.pages.len();
         self.pages.push(Page::new(new_page_id));
@@ -197,7 +198,7 @@ mod tests {
 
     #[test]
     fn test_arena_allocate_slice() {
-        let mut arena = MemoryArena::new();
+        let mut arena = MemoryArena::default();
         let a = b"hello";
         let b = b"happy tax payer";
 
@@ -220,7 +221,7 @@ mod tests {
 
     #[test]
     fn test_store_object() {
-        let mut arena = MemoryArena::new();
+        let mut arena = MemoryArena::default();
         let a = MyTest {
             a: 143,
             b: 21,