diff --git a/components/raftstore/src/engine_store_ffi/mod.rs b/components/raftstore/src/engine_store_ffi/mod.rs
index dd520a7b8f1..9016e478af9 100644
--- a/components/raftstore/src/engine_store_ffi/mod.rs
+++ b/components/raftstore/src/engine_store_ffi/mod.rs
@@ -27,13 +27,13 @@ use kvproto::{kvrpcpb, metapb, raft_cmdpb};
 use protobuf::Message;
 pub use read_index_helper::ReadIndexClient;
 
-pub use crate::engine_store_ffi::interfaces::root::DB::{
+pub use self::interfaces::root::DB::{
     BaseBuffView, ColumnFamilyType, CppStrVecView, EngineStoreApplyRes, EngineStoreServerHelper,
     EngineStoreServerStatus, FileEncryptionRes, FsStats, HttpRequestRes, HttpRequestStatus,
     KVGetStatus, RaftCmdHeader, RaftProxyStatus, RaftStoreProxyFFIHelper, RawCppPtr,
     RawCppStringPtr, RawVoidPtr, SSTReaderPtr, StoreStats, WriteCmdType, WriteCmdsView,
 };
-use crate::engine_store_ffi::{
+use self::{
     interfaces::root::DB::{
         ConstRawVoidPtr, FileEncryptionInfoRaw, RaftStoreProxyPtr, RawCppPtrType, RawRustPtr,
         SSTReaderInterfaces, SSTView, SSTViewVec, RAFT_STORE_PROXY_MAGIC_NUMBER,
@@ -276,7 +276,7 @@ impl Into<u32> for RawRustPtrType {
 
 pub extern "C" fn ffi_gc_rust_ptr(
     data: RawVoidPtr,
-    type_: crate::engine_store_ffi::interfaces::root::DB::RawRustPtrType,
+    type_: self::interfaces::root::DB::RawRustPtrType,
 ) {
     if data.is_null() {
         return;
@@ -385,9 +385,7 @@ pub extern "C" fn ffi_poll_read_index_task(
             _ => {}
         }
     }
-    let task = unsafe {
-        &mut *(task_ptr as *mut crate::engine_store_ffi::read_index_helper::ReadIndexTask)
-    };
+    let task = unsafe { &mut *(task_ptr as *mut self::read_index_helper::ReadIndexTask) };
     let waker = if std::ptr::null_mut() == waker {
         None
     } else {
diff --git a/components/raftstore/src/engine_store_ffi/observer.rs b/components/raftstore/src/engine_store_ffi/observer.rs
index cd1febb0653..e9892fa72df 100644
--- a/components/raftstore/src/engine_store_ffi/observer.rs
+++ b/components/raftstore/src/engine_store_ffi/observer.rs
@@ -737,6 +737,7 @@ impl ApplySnapshotObserver for TiFlashObserver {
                         info!("background pre-handle snapshot get error";
                             "snap_key" => ?snap_key,
                             "region" => ?ob_ctx.region(),
+                            "pending" => self.engine.pending_applies_count.load(Ordering::SeqCst),
                         );
                         true
                     }
@@ -754,6 +755,11 @@ impl ApplySnapshotObserver for TiFlashObserver {
             None => {
                 // We can't find background pre-handle task,
                 // maybe we can't get snapshot at that time.
+                info!("pre-handled snapshot not found";
+                    "snap_key" => ?snap_key,
+                    "region" => ?ob_ctx.region(),
+                    "pending" => self.engine.pending_applies_count.load(Ordering::SeqCst),
+                );
                 true
             }
         };
@@ -772,12 +778,12 @@ impl ApplySnapshotObserver for TiFlashObserver {
             );
             self.engine_store_server_helper
                 .apply_pre_handled_snapshot(ptr.0);
+            info!("apply snapshot finished";
+                "peer_id" => ?snap_key,
+                "region" => ?ob_ctx.region(),
+                "pending" => self.engine.pending_applies_count.load(Ordering::SeqCst),
+            );
         }
-        info!("apply snapshot finished";
-            "peer_id" => ?peer_id,
-            "region" => ?ob_ctx.region(),
-            "pending" => self.engine.pending_applies_count.load(Ordering::SeqCst),
-        );
         Ok(())
     }
 
diff --git a/components/raftstore/src/store/fsm/apply.rs b/components/raftstore/src/store/fsm/apply.rs
index 90800cca0aa..30f10f82dcf 100644
--- a/components/raftstore/src/store/fsm/apply.rs
+++ b/components/raftstore/src/store/fsm/apply.rs
@@ -75,9 +75,6 @@ use crate::{
         ApplyCtxInfo, Cmd, CmdBatch, CmdObserveInfo, CoprocessorHost, ObserveHandle, ObserveLevel,
         RegionState,
     },
-    engine_store_ffi::{
-        ColumnFamilyType, EngineStoreApplyRes, RaftCmdHeader, WriteCmdType, WriteCmds,
-    },
     store::{
         cmd_resp,
         fsm::RaftPollerBuilder,
diff --git a/components/raftstore/src/store/snap.rs b/components/raftstore/src/store/snap.rs
index abe8c60cd65..1001b1e2db1 100644
--- a/components/raftstore/src/store/snap.rs
+++ b/components/raftstore/src/store/snap.rs
@@ -45,7 +45,6 @@ use tikv_util::{
 
 use crate::{
     coprocessor::CoprocessorHost,
-    engine_store_ffi,
     store::{
         metrics::{
             CfNames, INGEST_SST_DURATION_SECONDS, SNAPSHOT_BUILD_TIME_HISTOGRAM,
@@ -450,14 +449,6 @@ pub struct Snapshot {
     mgr: SnapManagerCore,
 }
 
-pub struct PreHandledSnapshot {
-    pub index: u64,
-    pub term: u64,
-    pub inner: engine_store_ffi::RawCppPtr,
-}
-
-unsafe impl Send for PreHandledSnapshot {}
-
 #[derive(PartialEq, Eq, Clone, Copy)]
 enum CheckPolicy {
     ErrAllowed,
diff --git a/components/raftstore/src/store/worker/region.rs b/components/raftstore/src/store/worker/region.rs
index 19fc3714217..be34d30ad71 100644
--- a/components/raftstore/src/store/worker/region.rs
+++ b/components/raftstore/src/store/worker/region.rs
@@ -43,7 +43,7 @@ use crate::{
             JOB_STATUS_CANCELLED, JOB_STATUS_CANCELLING, JOB_STATUS_FAILED, JOB_STATUS_FINISHED,
             JOB_STATUS_PENDING, JOB_STATUS_RUNNING,
         },
-        snap::{plain_file_used, Error, PreHandledSnapshot, Result, SNAPSHOT_CFS},
+        snap::{plain_file_used, Error, Result, SNAPSHOT_CFS},
         transport::CasualRouter,
         ApplyOptions, CasualMessage, SnapEntry, SnapKey, SnapManager,
     },
@@ -119,8 +119,6 @@ struct EngineStoreApplySnapTask {
     region_id: u64,
     peer_id: u64,
     status: Arc<AtomicUsize>,
-    recv: mpsc::Receiver<Option<PreHandledSnapshot>>,
-    pre_handled_snap: Option<PreHandledSnapshot>,
 }
 
 #[derive(Clone)]
@@ -737,8 +735,8 @@ where
                 pool_size,
                 pre_handle_snap,
             },
-            pool: Builder::new(thd_name!("region-task"))
-                .max_thread_count(pool_size)
+            pool: Builder::new(thd_name!("snap-generator"))
+                .max_thread_count(snap_generator_pool_size)
                 .build_future_pool(),
             ctx: SnapContext {
                 engine,