diff --git a/src/stream/src/executor/stream_reader.rs b/src/stream/src/executor/stream_reader.rs
index 30de0804b0ac..57e80a0140c9 100644
--- a/src/stream/src/executor/stream_reader.rs
+++ b/src/stream/src/executor/stream_reader.rs
@@ -25,8 +25,34 @@ use crate::executor::Message;
 type ExecutorMessageStream = BoxStream<'static, StreamExecutorResult<Message>>;
 type StreamReaderData<M> = StreamExecutorResult<Either<Message, M>>;
 type ReaderArm<M> = BoxStream<'static, StreamReaderData<M>>;
-type StreamReaderWithPauseInner<M> =
-    SelectWithStrategy<ReaderArm<M>, ReaderArm<M>, impl FnMut(&mut PollNext) -> PollNext, PollNext>;
+
+mod stream_reader_with_pause {
+    use futures::stream::{select_with_strategy, PollNext, SelectWithStrategy};
+
+    use crate::executor::stream_reader::ReaderArm;
+
+    pub(super) type StreamReaderWithPauseInner<M, const BIASED: bool> = SelectWithStrategy<
+        ReaderArm<M>,
+        ReaderArm<M>,
+        impl FnMut(&mut PollNext) -> PollNext,
+        PollNext,
+    >;
+
+    pub(super) fn new_inner<M, const BIASED: bool>(
+        message_stream: ReaderArm<M>,
+        data_stream: ReaderArm<M>,
+    ) -> StreamReaderWithPauseInner<M, BIASED> {
+        let strategy = if BIASED {
+            |_: &mut PollNext| PollNext::Left
+        } else {
+            // The poll strategy is not biased: we poll the two streams in a round robin way.
+            |last: &mut PollNext| last.toggle()
+        };
+        select_with_strategy(message_stream, data_stream, strategy)
+    }
+}
+
+use stream_reader_with_pause::*;
 
 /// [`StreamReaderWithPause`] merges two streams, with one receiving barriers (and maybe other types
 /// of messages) and the other receiving data only (no barrier). The merged stream can be paused
@@ -40,7 +66,7 @@ type StreamReaderWithPauseInner<M> =
 /// priority over the right-hand one. Otherwise, the two streams will be polled in a round robin
 /// fashion.
 pub(super) struct StreamReaderWithPause<const BIASED: bool, M> {
-    inner: StreamReaderWithPauseInner<M>,
+    inner: StreamReaderWithPauseInner<M, BIASED>,
     /// Whether the source stream is paused.
     paused: bool,
 }
@@ -54,26 +80,13 @@ impl<const BIASED: bool, M: Send + 'static> StreamReaderWithPause<BIASED, M> {
     ) -> Self {
         let message_stream_arm = message_stream.map_ok(Either::Left).boxed();
         let data_stream_arm = data_stream.map_ok(Either::Right).boxed();
-        let inner = Self::new_inner(message_stream_arm, data_stream_arm);
+        let inner = new_inner(message_stream_arm, data_stream_arm);
         Self {
             inner,
             paused: false,
         }
     }
 
-    fn new_inner(
-        message_stream: ReaderArm<M>,
-        data_stream: ReaderArm<M>,
-    ) -> StreamReaderWithPauseInner<M> {
-        let strategy = if BIASED {
-            |_: &mut PollNext| PollNext::Left
-        } else {
-            // The poll strategy is not biased: we poll the two streams in a round robin way.
-            |last: &mut PollNext| last.toggle()
-        };
-        select_with_strategy(message_stream, data_stream, strategy)
-    }
-
     /// Replace the data stream with a new one for given `stream`. Used for split change.
     pub fn replace_data_stream(
         &mut self,
@@ -87,7 +100,7 @@ impl<const BIASED: bool, M: Send + 'static> StreamReaderWithPause<BIASED, M> {
 
         // Note: create a new `SelectWithStrategy` instead of replacing the source stream arm here,
         // to ensure the internal state of the `SelectWithStrategy` is reset. (#6300)
-        self.inner = Self::new_inner(
+        self.inner = new_inner(
             barrier_receiver_arm,
             data_stream.map_ok(Either::Right).boxed(),
         );
diff --git a/src/stream/src/task/barrier_manager/managed_state.rs b/src/stream/src/task/barrier_manager/managed_state.rs
index 43a979af2b56..5574966efdf5 100644
--- a/src/stream/src/task/barrier_manager/managed_state.rs
+++ b/src/stream/src/task/barrier_manager/managed_state.rs
@@ -88,8 +88,61 @@ pub(super) struct BarrierState {
     inner: ManagedBarrierStateInner,
 }
 
-type AwaitEpochCompletedFuture =
-    impl Future<Output = (Barrier, StreamResult<BarrierCompleteResult>)> + 'static;
+mod await_epoch_completed_future {
+    use std::future::Future;
+
+    use futures::future::BoxFuture;
+    use futures::FutureExt;
+    use risingwave_hummock_sdk::SyncResult;
+    use risingwave_pb::stream_service::barrier_complete_response::{
+        CreateMviewProgress, PbCreateMviewProgress,
+    };
+
+    use crate::error::StreamResult;
+    use crate::executor::Barrier;
+    use crate::task::{await_tree_key, BarrierCompleteResult};
+
+    pub(super) type AwaitEpochCompletedFuture =
+        impl Future<Output = (Barrier, StreamResult<BarrierCompleteResult>)> + 'static;
+
+    pub(super) fn instrument_complete_barrier_future(
+        complete_barrier_future: Option<BoxFuture<'static, StreamResult<SyncResult>>>,
+        barrier: Barrier,
+        barrier_await_tree_reg: Option<&await_tree::Registry>,
+        create_mview_progress: Vec<PbCreateMviewProgress>,
+    ) -> AwaitEpochCompletedFuture {
+        let prev_epoch = barrier.epoch.prev;
+        let future = async move {
+            if let Some(future) = complete_barrier_future {
+                let result = future.await;
+                result.map(Some)
+            } else {
+                Ok(None)
+            }
+        }
+        .map(move |result| {
+            (
+                barrier,
+                result.map(|sync_result| BarrierCompleteResult {
+                    sync_result,
+                    create_mview_progress,
+                }),
+            )
+        });
+        if let Some(reg) = barrier_await_tree_reg {
+            reg.register(
+                await_tree_key::BarrierAwait { prev_epoch },
+                format!("SyncEpoch({})", prev_epoch),
+            )
+            .instrument(future)
+            .left_future()
+        } else {
+            future.right_future()
+        }
+    }
+}
+
+use await_epoch_completed_future::*;
 
 fn sync_epoch<S: StateStore>(
     state_store: &S,
@@ -787,33 +840,12 @@ impl PartialGraphManagedBarrierState {
             let barrier = barrier_state.barrier.clone();
 
             self.await_epoch_completed_futures.push_back({
-                let future = async move {
-                    if let Some(future) = complete_barrier_future {
-                        let result = future.await;
-                        result.map(Some)
-                    } else {
-                        Ok(None)
-                    }
-                }
-                .map(move |result| {
-                    (
-                        barrier,
-                        result.map(|sync_result| BarrierCompleteResult {
-                            sync_result,
-                            create_mview_progress,
-                        }),
-                    )
-                });
-                if let Some(reg) = &self.barrier_await_tree_reg {
-                    reg.register(
-                        await_tree_key::BarrierAwait { prev_epoch },
-                        format!("SyncEpoch({})", prev_epoch),
-                    )
-                    .instrument(future)
-                    .left_future()
-                } else {
-                    future.right_future()
-                }
+                instrument_complete_barrier_future(
+                    complete_barrier_future,
+                    barrier,
+                    self.barrier_await_tree_reg.as_ref(),
+                    create_mview_progress,
+                )
             });
         }
     }