diff --git a/src/lib_shell/mempool_worker.ml b/src/lib_shell/mempool_worker.ml
index b5d303f36..2575a32d3 100644
--- a/src/lib_shell/mempool_worker.ml
+++ b/src/lib_shell/mempool_worker.ml
@@ -365,7 +365,7 @@ module Make(Static: STATIC)(Proto: Registered_protocol.T)
         parameters : parameters ;
       }
 
-    type view = { cache : ValidatedCache.t }
+    type view = { cache : Cache.t }
 
     let view (state : state) _ : view = { cache = state.cache }
 
@@ -374,7 +374,7 @@ module Make(Static: STATIC)(Proto: Registered_protocol.T)
       conv
         (fun { cache } -> cache)
         (fun cache -> { cache })
-        ValidatedCache.encoding
+        Cache.encoding
 
     let pp ppf _view =
       Format.fprintf ppf "lots of operations"
@@ -471,7 +471,7 @@ module Make(Static: STATIC)(Proto: Registered_protocol.T)
   (* this function update the internal state of the worker *)
   let validate_helper w parsed_op =
     let state = Worker.state w in
-    apply_operation state parsed_op >>= fun (validation_state, result) ->
+    apply_operation state parsed_op >>= fun (validation_state,result) ->
     begin
       match validation_state with
       | Some validation_state -> state.validation_state <- validation_state
@@ -491,14 +491,23 @@ module Make(Static: STATIC)(Proto: Registered_protocol.T)
   (* memoization is done only at on_* level *)
   let on_validate w parsed_op =
     let state = Worker.state w in
-    match ValidatedCache.find_opt state.cache parsed_op with
-    | None | Some ((Branch_delayed _),_) ->
-        validate_helper w parsed_op >>= fun result ->
-        ValidatedCache.add state.cache parsed_op (result, parsed_op.raw);
+    match Cache.find_validated_opt state.cache parsed_op with
+    | None | Some (Branch_delayed _) ->
+        validate_helper w parsed_op >>=? fun result ->
+        Cache.add_validated state.cache parsed_op result;
         (* operations are notified only the first time *)
         notify_helper w result parsed_op.raw ;
-        Lwt.return result
-    | Some (result,_) -> Lwt.return result
+        return result
+    | Some result -> return result
+
+  let on_parse w raw_op =
+    let state = Worker.state w in
+    match Cache.find_parsed_opt state.cache raw_op with
+    | None ->
+        parse_helper w raw_op >>= fun parsed_op ->
+        Cache.add_parsed state.cache raw_op parsed_op;
+        Lwt.return parsed_op
+    | Some parsed_op -> Lwt.return parsed_op
 
   (* worker's handlers *)
   let on_request :
@@ -508,13 +517,7 @@ module Make(Static: STATIC)(Proto: Registered_protocol.T)
 
   let on_launch (_ : t) (_ : Name.t) ( { chain_db ; validation_state } as parameters ) =
     let chain_state = Distributed_db.chain_state chain_db in
-    Chain.data chain_state >>= fun {
-      current_mempool = _mempool ;
-      live_blocks ; live_operations } ->
-    (* remove all operations that are already included *)
-    Operation_hash.Set.iter (fun hash ->
-        ParsedCache.rem parsed_cache hash
-      ) live_operations;
+    Chain.data chain_state >>= fun { current_mempool = _mempool ; live_blocks ; live_operations } ->
     Lwt.return {
       validation_state ;
       cache = ValidatedCache.create () ;
@@ -527,11 +530,11 @@ module Make(Static: STATIC)(Proto: Registered_protocol.T)
   let on_close w =
     let state = Worker.state w in
     Lwt_watcher.shutdown_input state.operation_stream;
-    ValidatedCache.iter (fun hash _ ->
+    Cache.iter_validated (fun hash _ ->
         Distributed_db.Operation.clear_or_cancel
           state.parameters.chain_db hash)
       state.cache ;
-    ValidatedCache.clear state.cache;
+    Cache.clear state.cache;
     Lwt.return_unit
 
   let on_error w r st errs =
@@ -591,7 +594,7 @@ module Make(Static: STATIC)(Proto: Registered_protocol.T)
       (Proto_services.S.Mempool.pending_operations RPC_path.open_root)
       (fun w () () ->
          let state = Worker.state w in
-         RPC_answer.return (ValidatedCache.to_mempool state.cache)
+         RPC_answer.return (Cache.to_mempool state.cache)
       )
 
   let monitor_rpc_directory : t RPC_directory.t =
@@ -602,19 +605,18 @@ module Make(Static: STATIC)(Proto: Registered_protocol.T)
          let state = Worker.state w in
          let filter_result = function
            | Applied _ -> params#applied
-           | Refused _ -> params#refused
-           | Branch_refused _ -> params#branch_refused
+           | Refused _ -> params#branch_refused
+           | Branch_refused _ -> params#refused
            | Branch_delayed _ -> params#branch_delayed
            | _ -> false in
 
          let op_stream, stopper = Lwt_watcher.create_stream state.operation_stream in
          let shutdown () = Lwt_watcher.shutdown stopper in
-         let rec next () =
+         let next () =
            Lwt_stream.get op_stream >>= function
            | Some (kind, shell, protocol_data) when filter_result kind ->
                Lwt.return_some [ { Proto.shell ; protocol_data } ]
-           | Some _ -> next ()
-           | None -> Lwt.return_none in
+           | _ -> Lwt.return_none in
          RPC_answer.return_stream { next ; shutdown }
       )