diff --git a/src/iterators/merge.rs b/src/iterators/merge.rs
index fe75ce7..36f7109 100644
--- a/src/iterators/merge.rs
+++ b/src/iterators/merge.rs
@@ -18,7 +18,7 @@ mod heap;
 /// iterators, prefer the one with smaller index.
 pub type MergeIterator<Item, I> = NoDuplication<MergeIteratorInner<Item, I>>;
 
-pub async fn create_merge_iter<Item, I>(iters: impl Stream<Item = Box<I>>) -> MergeIterator<Item, I>
+pub async fn create_merge_iter<Item, I>(iters: impl Stream<Item = I>) -> MergeIterator<Item, I>
 where
     Item: Ord + Debug,
     I: Stream<Item = anyhow::Result<Item>> + Unpin,
@@ -27,7 +27,7 @@ where
 }
 
 pub async fn create_merge_iter_from_non_empty_iters<Item, I>(
-    iters: impl Stream<Item = NonEmptyStream<Item, Box<I>>>,
+    iters: impl Stream<Item = NonEmptyStream<Item, I>>,
 ) -> MergeIterator<Item, I>
 where
     Item: Ord + Debug,
@@ -49,7 +49,7 @@ where
     I: Stream<Item = anyhow::Result<Item>> + Unpin,
     Item: Ord + Debug,
 {
-    pub async fn create(iters: impl Stream<Item = Box<I>>) -> Self {
+    pub async fn create(iters: impl Stream<Item = I>) -> Self {
         let iters = iters
             .map(NonEmptyStream::try_new)
             .flat_map(FutureExt::into_stream)
@@ -57,9 +57,7 @@ where
         Self::from_non_empty_iters(iters).await
     }
 
-    pub async fn from_non_empty_iters(
-        iters: impl Stream<Item = NonEmptyStream<Item, Box<I>>>,
-    ) -> Self {
+    pub async fn from_non_empty_iters(iters: impl Stream<Item = NonEmptyStream<Item, I>>) -> Self {
         let iters: BinaryHeap<_> = iters
             .enumerate()
             .map(|(index, iter)| HeapWrapper { index, iter })
diff --git a/src/iterators/merge/heap.rs b/src/iterators/merge/heap.rs
index 54240d9..492ce9d 100644
--- a/src/iterators/merge/heap.rs
+++ b/src/iterators/merge/heap.rs
@@ -3,7 +3,7 @@ use std::cmp;
 
 pub(super) struct HeapWrapper<Item, I> {
     pub index: usize,
-    pub iter: NonEmptyStream<Item, Box<I>>,
+    pub iter: NonEmptyStream<Item, I>,
 }
 
 impl<Item, I> HeapWrapper<Item, I>
diff --git a/src/memtable/iterator.rs b/src/memtable/iterator.rs
index d9eca7a..2f499f0 100644
--- a/src/memtable/iterator.rs
+++ b/src/memtable/iterator.rs
@@ -29,8 +29,8 @@ type SkipMapRangeIter<'a> = map::Range<'a, [u8], BytesBound<'a>, Bytes, Bytes>;
 
 type SkipMapRangeEntry<'a> = map::Entry<'a, Bytes, Bytes>;
 
-pub type NonEmptyMemTableIterRef<'a> = NonEmptyStream<Entry, Box<MemTableIterator<'a>>>;
-pub type MaybeEmptyMemTableIterRef<'a> = MaybeEmptyStream<Entry, Box<MemTableIterator<'a>>>;
+pub type NonEmptyMemTableIterRef<'a> = NonEmptyStream<Entry, MemTableIterator<'a>>;
+pub type MaybeEmptyMemTableIterRef<'a> = MaybeEmptyStream<Entry, MemTableIterator<'a>>;
 
 #[cfg(test)]
 mod test {
diff --git a/src/memtable/mutable.rs b/src/memtable/mutable.rs
index 7c50605..2169054 100644
--- a/src/memtable/mutable.rs
+++ b/src/memtable/mutable.rs
@@ -111,26 +111,15 @@ impl MemTable {
         lower: Bound<&'a [u8]>,
         upper: Bound<&'a [u8]>,
     ) -> Result<MaybeEmptyMemTableIterRef<'a>> {
-        let iter = foo(&self.map, lower, upper);
-        // let range = (lower, upper);
-        // let iter = self.map.range(range);
+        let iter = self.map.range(BytesBound {
+            start: lower,
+            end: upper,
+        });
         let iter = new_memtable_iter(iter);
-        NonEmptyStream::try_new(Box::new(iter)).await
+        NonEmptyStream::try_new(iter).await
     }
 }
 
-fn foo<'a, 'b>(
-    m: &'a SkipMap<Bytes, Bytes>,
-    lower: Bound<&'b [u8]>,
-    upper: Bound<&'b [u8]>,
-) -> Range<'a, [u8], BytesBound<'b>, Bytes, Bytes> {
-    let iter = m.range(BytesBound {
-        start: lower,
-        end: upper,
-    });
-    iter
-}
-
 #[cfg(test)]
 impl MemTable {
     pub fn for_testing_put_slice(&self, key: &[u8], value: &[u8]) -> Result<()> {
diff --git a/src/sst/sstables.rs b/src/sst/sstables.rs
index b74d37e..3c433f6 100644
--- a/src/sst/sstables.rs
+++ b/src/sst/sstables.rs
@@ -98,7 +98,7 @@ where
                         None
                     } else {
                         let iter = SsTableIterator::scan(table, lower, upper);
-                        NonEmptyStream::try_new(Box::new(iter)).await.ok().flatten()
+                        NonEmptyStream::try_new(iter).await.ok().flatten()
                     }
                 }
             });
@@ -106,14 +106,10 @@ where
         };
 
         let levels = {
-            let iters = self
-                .levels
-                .iter()
-                .filter_map(move |(_, ids)| {
-                    let tables = ids.iter().map(|id| self.sstables.get(id).unwrap());
-                    scan_sst_concat(tables, lower, upper).ok()
-                })
-                .map(Box::new);
+            let iters = self.levels.iter().filter_map(move |(_, ids)| {
+                let tables = ids.iter().map(|id| self.sstables.get(id).unwrap());
+                scan_sst_concat(tables, lower, upper).ok()
+            });
             let iters = stream::iter(iters);
             create_merge_iter(iters).await
         };