diff --git a/src/core/index_meta.rs b/src/core/index_meta.rs
index c5d33e370..8927c5403 100644
--- a/src/core/index_meta.rs
+++ b/src/core/index_meta.rs
@@ -2,6 +2,7 @@ use core::SegmentMeta;
 use schema::Schema;
 use serde_json;
 use std::fmt;
+use Opstamp;
 
 /// Meta information about the `Index`.
 ///
@@ -15,7 +16,7 @@ use std::fmt;
 pub struct IndexMeta {
     pub segments: Vec<SegmentMeta>,
     pub schema: Schema,
-    pub opstamp: u64,
+    pub opstamp: Opstamp,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub payload: Option<String>,
 }
diff --git a/src/core/segment.rs b/src/core/segment.rs
index a747cfaec..b87208fcb 100644
--- a/src/core/segment.rs
+++ b/src/core/segment.rs
@@ -10,6 +10,7 @@ use schema::Schema;
 use std::fmt;
 use std::path::PathBuf;
 use std::result;
+use Opstamp;
 use Result;
 
 /// A segment is a piece of the index.
@@ -50,7 +51,7 @@ impl Segment {
     }
 
     #[doc(hidden)]
-    pub fn with_delete_meta(self, num_deleted_docs: u32, opstamp: u64) -> Segment {
+    pub fn with_delete_meta(self, num_deleted_docs: u32, opstamp: Opstamp) -> Segment {
         Segment {
             index: self.index,
             meta: self.meta.with_delete_meta(num_deleted_docs, opstamp),
diff --git a/src/core/segment_meta.rs b/src/core/segment_meta.rs
index 9478663ea..2f4b4177e 100644
--- a/src/core/segment_meta.rs
+++ b/src/core/segment_meta.rs
@@ -5,6 +5,7 @@ use serde;
 use std::collections::HashSet;
 use std::fmt;
 use std::path::PathBuf;
+use Opstamp;
 
 lazy_static! {
     static ref INVENTORY: Inventory<InnerSegmentMeta> = { Inventory::new() };
@@ -13,7 +14,7 @@ lazy_static! {
 #[derive(Clone, Debug, Serialize, Deserialize)]
 struct DeleteMeta {
     num_deleted_docs: u32,
-    opstamp: u64,
+    opstamp: Opstamp,
 }
 
 /// `SegmentMeta` contains simple meta information about a segment.
@@ -136,9 +137,9 @@ impl SegmentMeta {
         self.max_doc() - self.num_deleted_docs()
     }
 
-    /// Returns the opstamp of the last delete operation
+    /// Returns the `Opstamp` of the last delete operation
     /// taken in account in this segment.
-    pub fn delete_opstamp(&self) -> Option<u64> {
+    pub fn delete_opstamp(&self) -> Option<Opstamp> {
         self.tracked
             .deletes
             .as_ref()
@@ -152,7 +153,7 @@ impl SegmentMeta {
     }
 
     #[doc(hidden)]
-    pub fn with_delete_meta(self, num_deleted_docs: u32, opstamp: u64) -> SegmentMeta {
+    pub fn with_delete_meta(self, num_deleted_docs: u32, opstamp: Opstamp) -> SegmentMeta {
         let delete_meta = DeleteMeta {
             num_deleted_docs,
             opstamp,
diff --git a/src/indexer/delete_queue.rs b/src/indexer/delete_queue.rs
index be36bef7a..595691f98 100644
--- a/src/indexer/delete_queue.rs
+++ b/src/indexer/delete_queue.rs
@@ -2,6 +2,7 @@ use super::operation::DeleteOperation;
 use std::mem;
 use std::ops::DerefMut;
 use std::sync::{Arc, RwLock};
+use Opstamp;
 
 // The DeleteQueue is similar in conceptually to a multiple
 // consumer single producer broadcast channel.
@@ -184,7 +185,7 @@ impl DeleteCursor {
     ///   queue are consume and the next get will return None.
     /// - the next get will return the first operation with an
     /// `opstamp >= target_opstamp`.
-    pub fn skip_to(&mut self, target_opstamp: u64) {
+    pub fn skip_to(&mut self, target_opstamp: Opstamp) {
         // TODO Can be optimize as we work with block.
         while self.is_behind_opstamp(target_opstamp) {
             self.advance();
@@ -192,7 +193,7 @@ impl DeleteCursor {
     }
 
     #[cfg_attr(feature = "cargo-clippy", allow(clippy::wrong_self_convention))]
-    fn is_behind_opstamp(&mut self, target_opstamp: u64) -> bool {
+    fn is_behind_opstamp(&mut self, target_opstamp: Opstamp) -> bool {
         self.get()
             .map(|operation| operation.opstamp < target_opstamp)
             .unwrap_or(false)
diff --git a/src/indexer/doc_opstamp_mapping.rs b/src/indexer/doc_opstamp_mapping.rs
index 26bbe4c2f..d616800ab 100644
--- a/src/indexer/doc_opstamp_mapping.rs
+++ b/src/indexer/doc_opstamp_mapping.rs
@@ -1,5 +1,6 @@
 use std::sync::Arc;
 use DocId;
+use Opstamp;
 
 // Doc to opstamp is used to identify which
 // document should be deleted.
@@ -23,7 +24,7 @@ pub enum DocToOpstampMapping {
 }
 
 impl From<Vec<u64>> for DocToOpstampMapping {
-    fn from(opstamps: Vec<u64>) -> DocToOpstampMapping {
+    fn from(opstamps: Vec<Opstamp>) -> DocToOpstampMapping {
         DocToOpstampMapping::WithMap(Arc::new(opstamps))
     }
 }
@@ -35,7 +36,7 @@ impl DocToOpstampMapping {
     //
     // The edge case opstamp = some doc opstamp is in practise
     // never called.
-    pub fn compute_doc_limit(&self, target_opstamp: u64) -> DocId {
+    pub fn compute_doc_limit(&self, target_opstamp: Opstamp) -> DocId {
         match *self {
             DocToOpstampMapping::WithMap(ref doc_opstamps) => {
                 match doc_opstamps.binary_search(&target_opstamp) {
diff --git a/src/indexer/index_writer.rs b/src/indexer/index_writer.rs
index 94961f5fc..398e61358 100644
--- a/src/indexer/index_writer.rs
+++ b/src/indexer/index_writer.rs
@@ -30,6 +30,7 @@ use std::ops::Range;
 use std::sync::Arc;
 use std::thread;
 use std::thread::JoinHandle;
+use Opstamp;
 use Result;
 
 // Size of the margin for the heap. A segment is closed when the remaining memory
@@ -99,7 +100,7 @@ pub struct IndexWriter {
     delete_queue: DeleteQueue,
 
     stamper: Stamper,
-    committed_opstamp: u64,
+    committed_opstamp: Opstamp,
 }
 
 /// Open a new index writer. Attempts to acquire a lockfile.
@@ -177,7 +178,7 @@ pub fn compute_deleted_bitset(
     segment_reader: &SegmentReader,
     delete_cursor: &mut DeleteCursor,
     doc_opstamps: &DocToOpstampMapping,
-    target_opstamp: u64,
+    target_opstamp: Opstamp,
 ) -> Result<bool> {
     let mut might_have_changed = false;
 
@@ -219,7 +220,7 @@ pub fn compute_deleted_bitset(
 pub fn advance_deletes(
     mut segment: Segment,
     segment_entry: &mut SegmentEntry,
-    target_opstamp: u64,
+    target_opstamp: Opstamp,
 ) -> Result<()> {
     {
         if segment_entry.meta().delete_opstamp() == Some(target_opstamp) {
@@ -299,11 +300,11 @@ fn index_documents(
     // the worker thread.
     assert!(num_docs > 0);
 
-    let doc_opstamps: Vec<u64> = segment_writer.finalize()?;
+    let doc_opstamps: Vec<Opstamp> = segment_writer.finalize()?;
 
     let segment_meta = SegmentMeta::new(segment_id, num_docs);
 
-    let last_docstamp: u64 = *(doc_opstamps.last().unwrap());
+    let last_docstamp: Opstamp = *(doc_opstamps.last().unwrap());
 
     let delete_bitset_opt = if delete_cursor.get().is_some() {
         let doc_to_opstamps = DocToOpstampMapping::from(doc_opstamps);
@@ -494,7 +495,7 @@ impl IndexWriter {
     /// state as it was after the last commit.
     ///
     /// The opstamp at the last commit is returned.
-    pub fn rollback(&mut self) -> Result<()> {
+    pub fn rollback(&mut self) -> Result<Opstamp> {
         info!("Rolling back to opstamp {}", self.committed_opstamp);
 
         // marks the segment updater as killed. From now on, all
@@ -529,7 +530,7 @@ impl IndexWriter {
         // was dropped with the index_writer.
         for _ in document_receiver.clone() {}
 
-        Ok(())
+        Ok(self.committed_opstamp)
     }
 
     /// Prepares a commit.
@@ -567,7 +568,7 @@ impl IndexWriter {
         info!("Preparing commit");
 
         // this will drop the current document channel
-        // and recreate a new one channels.
+        // and recreate a new one.
         self.recreate_document_channel();
 
         let former_workers_join_handle = mem::replace(&mut self.workers_join_handle, Vec::new());
@@ -601,7 +602,7 @@ impl IndexWriter {
     /// Commit returns the `opstamp` of the last document
     /// that made it in the commit.
     ///
-    pub fn commit(&mut self) -> Result<u64> {
+    pub fn commit(&mut self) -> Result<Opstamp> {
         self.prepare_commit()?.commit()
     }
 
@@ -617,7 +618,7 @@ impl IndexWriter {
     ///
     /// Like adds, the deletion itself will be visible
     /// only after calling `commit()`.
-    pub fn delete_term(&mut self, term: Term) -> u64 {
+    pub fn delete_term(&mut self, term: Term) -> Opstamp {
         let opstamp = self.stamper.stamp();
         let delete_operation = DeleteOperation { opstamp, term };
         self.delete_queue.push(delete_operation);
@@ -631,7 +632,7 @@ impl IndexWriter {
     ///
     /// This is also the opstamp of the commit that is currently
     /// available for searchers.
-    pub fn commit_opstamp(&self) -> u64 {
+    pub fn commit_opstamp(&self) -> Opstamp {
         self.committed_opstamp
     }
 
@@ -645,7 +646,7 @@ impl IndexWriter {
     ///
     /// Currently it represents the number of documents that
     /// have been added since the creation of the index.
-    pub fn add_document(&mut self, document: Document) -> u64 {
+    pub fn add_document(&mut self, document: Document) -> Opstamp {
         let opstamp = self.stamper.stamp();
         let add_operation = AddOperation { opstamp, document };
         let send_result = self.operation_sender.send(vec![add_operation]);
@@ -662,7 +663,7 @@ impl IndexWriter {
     /// The total number of stamps generated by this method is `count + 1`;
     /// each operation gets a stamp from the `stamps` iterator and `last_opstamp`
     /// is for the batch itself.
-    fn get_batch_opstamps(&mut self, count: u64) -> (u64, Range<u64>) {
+    fn get_batch_opstamps(&mut self, count: Opstamp) -> (Opstamp, Range<Opstamp>) {
         let Range { start, end } = self.stamper.stamps(count + 1u64);
         let last_opstamp = end - 1;
         let stamps = Range {
@@ -688,7 +689,7 @@ impl IndexWriter {
     /// Like adds and deletes (see `IndexWriter.add_document` and
     /// `IndexWriter.delete_term`), the changes made by calling `run` will be
     /// visible to readers only after calling `commit()`.
-    pub fn run(&mut self, user_operations: Vec<UserOperation>) -> u64 {
+    pub fn run(&mut self, user_operations: Vec<UserOperation>) -> Opstamp {
         let count = user_operations.len() as u64;
         if count == 0 {
             return self.stamper.stamp();
diff --git a/src/indexer/merge_operation.rs b/src/indexer/merge_operation.rs
index 9d7bcbca6..0474fefd8 100644
--- a/src/indexer/merge_operation.rs
+++ b/src/indexer/merge_operation.rs
@@ -1,5 +1,6 @@
 use census::{Inventory, TrackedObject};
 use std::collections::HashSet;
+use Opstamp;
 use SegmentId;
 
 #[derive(Default)]
@@ -17,8 +18,8 @@ impl MergeOperationInventory {
     }
 }
 
-/// A `MergeOperation` has two role.
-/// It carries all of the information required to describe a merge :
+/// A `MergeOperation` has two roles.
+/// It carries all of the information required to describe a merge:
 /// - `target_opstamp` is the opstamp up to which we want to consume the
 /// delete queue and reflect their deletes.
 /// - `segment_ids` is the list of segment to be merged.
@@ -35,14 +36,14 @@ pub struct MergeOperation {
 }
 
 struct InnerMergeOperation {
-    target_opstamp: u64,
+    target_opstamp: Opstamp,
     segment_ids: Vec<SegmentId>,
 }
 
 impl MergeOperation {
     pub fn new(
         inventory: &MergeOperationInventory,
-        target_opstamp: u64,
+        target_opstamp: Opstamp,
         segment_ids: Vec<SegmentId>,
     ) -> MergeOperation {
         let inner_merge_operation = InnerMergeOperation {
@@ -54,7 +55,7 @@ impl MergeOperation {
         }
     }
 
-    pub fn target_opstamp(&self) -> u64 {
+    pub fn target_opstamp(&self) -> Opstamp {
         self.inner.target_opstamp
     }
 
diff --git a/src/indexer/operation.rs b/src/indexer/operation.rs
index fe57a4a3a..03bfabb59 100644
--- a/src/indexer/operation.rs
+++ b/src/indexer/operation.rs
@@ -1,17 +1,18 @@
 use schema::Document;
 use schema::Term;
+use Opstamp;
 
 /// Timestamped Delete operation.
 #[derive(Clone, Eq, PartialEq, Debug)]
 pub struct DeleteOperation {
-    pub opstamp: u64,
+    pub opstamp: Opstamp,
     pub term: Term,
 }
 
 /// Timestamped Add operation.
 #[derive(Eq, PartialEq, Debug)]
 pub struct AddOperation {
-    pub opstamp: u64,
+    pub opstamp: Opstamp,
     pub document: Document,
 }
 
diff --git a/src/indexer/prepared_commit.rs b/src/indexer/prepared_commit.rs
index 4728af01a..92f47cdfd 100644
--- a/src/indexer/prepared_commit.rs
+++ b/src/indexer/prepared_commit.rs
@@ -1,15 +1,16 @@
 use super::IndexWriter;
+use Opstamp;
 use Result;
 
 /// A prepared commit
 pub struct PreparedCommit<'a> {
     index_writer: &'a mut IndexWriter,
     payload: Option<String>,
-    opstamp: u64,
+    opstamp: Opstamp,
 }
 
 impl<'a> PreparedCommit<'a> {
-    pub(crate) fn new(index_writer: &'a mut IndexWriter, opstamp: u64) -> PreparedCommit {
+    pub(crate) fn new(index_writer: &'a mut IndexWriter, opstamp: Opstamp) -> PreparedCommit {
         PreparedCommit {
             index_writer,
             payload: None,
@@ -17,7 +18,7 @@ impl<'a> PreparedCommit<'a> {
         }
     }
 
-    pub fn opstamp(&self) -> u64 {
+    pub fn opstamp(&self) -> Opstamp {
         self.opstamp
     }
 
@@ -25,11 +26,11 @@ impl<'a> PreparedCommit<'a> {
         self.payload = Some(payload.to_string())
     }
 
-    pub fn abort(self) -> Result<()> {
+    pub fn abort(self) -> Result<Opstamp> {
         self.index_writer.rollback()
     }
 
-    pub fn commit(self) -> Result<u64> {
+    pub fn commit(self) -> Result<Opstamp> {
         info!("committing {}", self.opstamp);
         self.index_writer
             .segment_updater()
diff --git a/src/indexer/segment_updater.rs b/src/indexer/segment_updater.rs
index 316dbd68a..4dd7a6804 100644
--- a/src/indexer/segment_updater.rs
+++ b/src/indexer/segment_updater.rs
@@ -36,6 +36,7 @@ use std::sync::Arc;
 use std::sync::RwLock;
 use std::thread;
 use std::thread::JoinHandle;
+use Opstamp;
 use Result;
 
 /// Save the index meta file.
@@ -224,7 +225,7 @@ impl SegmentUpdater {
     ///
     /// Tne method returns copies of the segment entries,
     /// updated with the delete information.
-    fn purge_deletes(&self, target_opstamp: u64) -> Result<Vec<SegmentEntry>> {
+    fn purge_deletes(&self, target_opstamp: Opstamp) -> Result<Vec<SegmentEntry>> {
         let mut segment_entries = self.0.segment_manager.segment_entries();
         for segment_entry in &mut segment_entries {
             let segment = self.0.index.segment(segment_entry.meta().clone());
@@ -233,7 +234,7 @@ impl SegmentUpdater {
         Ok(segment_entries)
     }
 
-    pub fn save_metas(&self, opstamp: u64, commit_message: Option<String>) {
+    pub fn save_metas(&self, opstamp: Opstamp, commit_message: Option<String>) {
         if self.is_alive() {
             let index = &self.0.index;
             let directory = index.directory();
@@ -280,7 +281,7 @@ impl SegmentUpdater {
             .garbage_collect(|| self.0.segment_manager.list_files());
     }
 
-    pub fn commit(&self, opstamp: u64, payload: Option<String>) -> Result<()> {
+    pub fn commit(&self, opstamp: Opstamp, payload: Option<String>) -> Result<()> {
         self.run_async(move |segment_updater| {
             if segment_updater.is_alive() {
                 let segment_entries = segment_updater
diff --git a/src/indexer/segment_writer.rs b/src/indexer/segment_writer.rs
index 41fab5a6e..a7da06fd1 100644
--- a/src/indexer/segment_writer.rs
+++ b/src/indexer/segment_writer.rs
@@ -16,6 +16,7 @@ use tokenizer::BoxedTokenizer;
 use tokenizer::FacetTokenizer;
 use tokenizer::{TokenStream, Tokenizer};
 use DocId;
+use Opstamp;
 use Result;
 
 /// A `SegmentWriter` is in charge of creating segment index from a
@@ -29,7 +30,7 @@ pub struct SegmentWriter {
     segment_serializer: SegmentSerializer,
     fast_field_writers: FastFieldsWriter,
     fieldnorms_writer: FieldNormsWriter,
-    doc_opstamps: Vec<u64>,
+    doc_opstamps: Vec<Opstamp>,
     tokenizers: Vec<Option<Box<BoxedTokenizer>>>,
 }
 
diff --git a/src/indexer/stamper.rs b/src/indexer/stamper.rs
index 6cd1c494a..631cbb527 100644
--- a/src/indexer/stamper.rs
+++ b/src/indexer/stamper.rs
@@ -1,70 +1,27 @@
 use std::ops::Range;
-use std::sync::atomic::Ordering;
+use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::Arc;
+use Opstamp;
 
-// AtomicU64 have not landed in stable.
-// For the moment let's just use AtomicUsize on
-// x86/64 bit platform, and a mutex on other platform.
-#[cfg(target_arch = "x86_64")]
-mod archicture_impl {
-
-    use std::sync::atomic::{AtomicUsize, Ordering};
-
-    #[derive(Default)]
-    pub struct AtomicU64Ersatz(AtomicUsize);
-
-    impl AtomicU64Ersatz {
-        pub fn new(first_opstamp: u64) -> AtomicU64Ersatz {
-            AtomicU64Ersatz(AtomicUsize::new(first_opstamp as usize))
-        }
-
-        pub fn fetch_add(&self, val: u64, order: Ordering) -> u64 {
-            self.0.fetch_add(val as usize, order) as u64
-        }
-    }
-}
-
-#[cfg(not(target_arch = "x86_64"))]
-mod archicture_impl {
-
-    use std::sync::atomic::Ordering;
-    /// Under other architecture, we rely on a mutex.
-    use std::sync::RwLock;
-
-    #[derive(Default)]
-    pub struct AtomicU64Ersatz(RwLock<u64>);
-
-    impl AtomicU64Ersatz {
-        pub fn new(first_opstamp: u64) -> AtomicU64Ersatz {
-            AtomicU64Ersatz(RwLock::new(first_opstamp))
-        }
-
-        pub fn fetch_add(&self, incr: u64, _order: Ordering) -> u64 {
-            let mut lock = self.0.write().unwrap();
-            let previous_val = *lock;
-            *lock = previous_val + incr;
-            previous_val
-        }
-    }
-}
-
-use self::archicture_impl::AtomicU64Ersatz;
-
+/// Stamper provides Opstamps, which is just an auto-increment id to label
+/// an operation.
+///
+/// Cloning does not "fork" the stamp generation. The stamper actually wraps an `Arc`.
 #[derive(Clone, Default)]
-pub struct Stamper(Arc<AtomicU64Ersatz>);
+pub struct Stamper(Arc<AtomicU64>);
 
 impl Stamper {
-    pub fn new(first_opstamp: u64) -> Stamper {
-        Stamper(Arc::new(AtomicU64Ersatz::new(first_opstamp)))
+    pub fn new(first_opstamp: Opstamp) -> Stamper {
+        Stamper(Arc::new(AtomicU64::new(first_opstamp)))
     }
 
-    pub fn stamp(&self) -> u64 {
+    pub fn stamp(&self) -> Opstamp {
         self.0.fetch_add(1u64, Ordering::SeqCst) as u64
     }
 
     /// Given a desired count `n`, `stamps` returns an iterator that
     /// will supply `n` number of u64 stamps.
-    pub fn stamps(&self, n: u64) -> Range<u64> {
+    pub fn stamps(&self, n: u64) -> Range<Opstamp> {
         let start = self.0.fetch_add(n, Ordering::SeqCst);
         Range {
             start,
@@ -92,4 +49,5 @@ mod test {
         assert_eq!(stamper.stamps(3u64), (12..15));
         assert_eq!(stamper.stamp(), 15u64);
     }
+
 }
diff --git a/src/lib.rs b/src/lib.rs
index 4f0e50a0d..63c9f6929 100755
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -254,6 +254,16 @@ pub mod merge_policy {
 /// as they are added in the segment.
 pub type DocId = u32;
 
+/// A u64 assigned to every operation incrementally
+///
+/// All operations modifying the index receives an monotonic Opstamp.
+/// The resulting state of the index is consistent with the opstamp ordering.
+///
+/// For instance, a commit with opstamp `32_423` will reflect all Add and Delete operations
+/// with an opstamp `<= 32_423`. A delete operation with opstamp n will no affect a document added
+/// with opstamp `n+1`.
+pub type Opstamp = u64;
+
 /// A f32 that represents the relevance of the document to the query
 ///
 /// This is modelled internally as a `f32`. The