diff --git a/db/db_iter.cc b/db/db_iter.cc
index 541a5fbed..df2be1b7c 100644
--- a/db/db_iter.cc
+++ b/db/db_iter.cc
@@ -231,7 +231,7 @@ class DBIter final: public Iterator {
     return Status::InvalidArgument("Unidentified property.");
   }
 
-  void Next() override;
+  void Next() final override;
   void Prev() override;
   void Seek(const Slice& target) override;
   void SeekForPrev(const Slice& target) override;
diff --git a/db/version_set.cc b/db/version_set.cc
index 1295baf7e..e916fed6e 100644
--- a/db/version_set.cc
+++ b/db/version_set.cc
@@ -906,7 +906,8 @@ class LevelIterator final : public InternalIterator {
   void SeekForPrev(const Slice& target) override;
   void SeekToFirst() override;
   void SeekToLast() override;
-  void Next() override;
+  void Next() final override;
+  bool NextAndGetResult(Slice* ret_key) override;
   void Prev() override;
 
   bool Valid() const override { return file_iter_.Valid(); }
@@ -942,6 +943,13 @@ class LevelIterator final : public InternalIterator {
   void SetFileIterator(InternalIterator* iter);
   void InitFileIterator(size_t new_file_index);
 
+  // Called by both of Next() and NextAndGetResult(). Force inline.
+  void NextImpl() {
+    assert(Valid());
+    file_iter_.Next();
+    SkipEmptyFileForward();
+  }
+
   const Slice& file_smallest_key(size_t file_index) {
     assert(file_index < flevel_->num_files);
     return flevel_->files[file_index].smallest_key;
@@ -1037,10 +1045,15 @@ void LevelIterator::SeekToLast() {
   SkipEmptyFileBackward();
 }
 
-void LevelIterator::Next() {
-  assert(Valid());
-  file_iter_.Next();
-  SkipEmptyFileForward();
+void LevelIterator::Next() { NextImpl(); }
+
+bool LevelIterator::NextAndGetResult(Slice* ret_key) {
+  NextImpl();
+  bool is_valid = Valid();
+  if (is_valid) {
+    *ret_key = key();
+  }
+  return is_valid;
 }
 
 void LevelIterator::Prev() {
diff --git a/table/block.h b/table/block.h
index 7ef001d58..df4d4eb82 100644
--- a/table/block.h
+++ b/table/block.h
@@ -392,7 +392,7 @@ class DataBlockIter final : public BlockIter<Slice> {
 
   virtual void Prev() override;
 
-  virtual void Next() override;
+  virtual void Next() final override;
 
   // Try to advance to the next entry in the block. If there is data corruption
   // or error, report it to the caller instead of aborting the process. May
diff --git a/table/block_based_table_reader.cc b/table/block_based_table_reader.cc
index c6ceacdcb..9db053842 100644
--- a/table/block_based_table_reader.cc
+++ b/table/block_based_table_reader.cc
@@ -2435,6 +2435,17 @@ void BlockBasedTableIterator<TBlockIter, TValue>::Next() {
   FindKeyForward();
 }
 
+template <class TBlockIter, typename TValue>
+bool BlockBasedTableIterator<TBlockIter, TValue>::NextAndGetResult(
+    Slice* ret_key) {
+  Next();
+  bool is_valid = Valid();
+  if (is_valid) {
+    *ret_key = key();
+  }
+  return is_valid;
+}
+
 template <class TBlockIter, typename TValue>
 void BlockBasedTableIterator<TBlockIter, TValue>::Prev() {
   assert(block_iter_points_to_real_block_);
@@ -2493,10 +2504,10 @@ void BlockBasedTableIterator<TBlockIter, TValue>::InitDataBlock() {
 }
 
 template <class TBlockIter, typename TValue>
-void BlockBasedTableIterator<TBlockIter, TValue>::FindKeyForward() {
+void BlockBasedTableIterator<TBlockIter, TValue>::FindBlockForward() {
   // TODO the while loop inherits from two-level-iterator. We don't know
   // whether a block can be empty so it can be replaced by an "if".
-  while (!block_iter_.Valid()) {
+  do {
     if (!block_iter_.status().ok()) {
       return;
     }
@@ -2528,6 +2539,15 @@ void BlockBasedTableIterator<TBlockIter, TValue>::FindKeyForward() {
     } else {
       return;
     }
+  } while (!block_iter_.Valid());
+}
+
+template <class TBlockIter, typename TValue>
+void BlockBasedTableIterator<TBlockIter, TValue>::FindKeyForward() {
+  assert(!is_out_of_bound_);
+
+  if (!block_iter_.Valid()) {
+    FindBlockForward();
   }
 }
 
diff --git a/table/block_based_table_reader.h b/table/block_based_table_reader.h
index 82fe3c888..ea8ba62c5 100644
--- a/table/block_based_table_reader.h
+++ b/table/block_based_table_reader.h
@@ -611,7 +611,8 @@ class BlockBasedTableIterator : public InternalIteratorBase<TValue> {
   void SeekForPrev(const Slice& target) override;
   void SeekToFirst() override;
   void SeekToLast() override;
-  void Next() override;
+  void Next() final override;
+  bool NextAndGetResult(Slice* ret_key) override;
   void Prev() override;
   bool Valid() const override {
     return !is_out_of_bound_ && block_iter_points_to_real_block_ &&
@@ -688,7 +689,8 @@ class BlockBasedTableIterator : public InternalIteratorBase<TValue> {
   }
 
   void InitDataBlock();
-  void FindKeyForward();
+  inline void FindKeyForward();
+  void FindBlockForward();
   void FindKeyBackward();
   void CheckOutOfBound();
 
diff --git a/table/internal_iterator.h b/table/internal_iterator.h
index d08fcae25..6b713e7b9 100644
--- a/table/internal_iterator.h
+++ b/table/internal_iterator.h
@@ -54,6 +54,15 @@ class InternalIteratorBase : public Cleanable {
   // REQUIRES: Valid()
   virtual void Next() = 0;
 
+  virtual bool NextAndGetResult(Slice* ret_key) {
+    Next();
+    bool is_valid = Valid();
+    if (is_valid) {
+      *ret_key = key();
+    }
+    return is_valid;
+  }
+
   // Moves to the previous entry in the source.  After this call, Valid() is
   // true iff the iterator was not positioned at the first entry in source.
   // REQUIRES: Valid()
diff --git a/table/iterator_wrapper.h b/table/iterator_wrapper.h
index 5941b846a..fc5eb2613 100644
--- a/table/iterator_wrapper.h
+++ b/table/iterator_wrapper.h
@@ -63,7 +63,11 @@ class IteratorWrapperBase {
   }
   // Methods below require iter() != nullptr
   Status status() const     { assert(iter_); return iter_->status(); }
-  void Next()               { assert(iter_); iter_->Next();        Update(); }
+  void Next() {
+    assert(iter_);
+    valid_ = iter_->NextAndGetResult(&key_);
+    assert(!valid_ || iter_->status().ok());
+  }
   void Prev()               { assert(iter_); iter_->Prev();        Update(); }
   void Seek(const Slice& k) { assert(iter_); iter_->Seek(k);       Update(); }
   void SeekForPrev(const Slice& k) {