diff --git a/db/compaction_picker.cc b/db/compaction_picker.cc
index fa2fbc663..8dd3c03bf 100644
--- a/db/compaction_picker.cc
+++ b/db/compaction_picker.cc
@@ -132,26 +132,16 @@ void CompactionPicker::GetRange(const std::vector<FileMetaData*>& inputs1,
   GetRange(all, smallest, largest);
 }
 
-// Add more files to the inputs on "level" to make sure that
-// no newer version of a key is compacted to "level+1" while leaving an older
-// version in a "level". Otherwise, any Get() will search "level" first,
-// and will likely return an old/stale value for the key, since it always
-// searches in increasing order of level to find the value. This could
-// also scramble the order of merge operands. This function should be
-// called any time a new Compaction is created, and its inputs_[0] are
-// populated.
-//
-// Will set c to nullptr if it is impossible to apply this compaction.
-void CompactionPicker::ExpandWhileOverlapping(Compaction* c) {
+bool CompactionPicker::ExpandWhileOverlapping(Compaction* c) {
   // If inputs are empty then there is nothing to expand.
   if (!c || c->inputs_[0].empty()) {
-    return;
+    return true;
   }
 
   // GetOverlappingInputs will always do the right thing for level-0.
   // So we don't need to do any expansion if level == 0.
   if (c->level() == 0) {
-    return;
+    return true;
   }
 
   const int level = c->level();
@@ -182,9 +172,9 @@ void CompactionPicker::ExpandWhileOverlapping(Compaction* c) {
                                &parent_index))) {
     c->inputs_[0].clear();
     c->inputs_[1].clear();
-    delete c;
-    c = nullptr;
+    return false;
   }
+  return true;
 }
 
 uint64_t CompactionPicker::ExpandedCompactionByteSizeLimit(int level) {
@@ -341,8 +331,8 @@ Compaction* CompactionPicker::CompactRange(Version* version, int input_level,
                                  MaxGrandParentOverlapBytes(input_level));
 
   c->inputs_[0] = inputs;
-  ExpandWhileOverlapping(c);
-  if (c == nullptr) {
+  if (ExpandWhileOverlapping(c) == false) {
+    delete c;
     Log(options_->info_log, "Could not compact due to expansion failure.\n");
     return nullptr;
   }
@@ -383,8 +373,10 @@ Compaction* LevelCompactionPicker::PickCompaction(Version* version) {
     level = version->compaction_level_[i];
     if ((version->compaction_score_[i] >= 1)) {
       c = PickCompactionBySize(version, level, version->compaction_score_[i]);
-      ExpandWhileOverlapping(c);
-      if (c != nullptr) {
+      if (ExpandWhileOverlapping(c) == false) {
+        delete c;
+        c = nullptr;
+      } else {
         break;
       }
     }
@@ -408,7 +400,9 @@ Compaction* LevelCompactionPicker::PickCompaction(Version* version) {
         c->inputs_[0].push_back(f);
         c->parent_index_ = parent_index;
         c->input_version_->file_to_compact_ = nullptr;
-        ExpandWhileOverlapping(c);
+        if (ExpandWhileOverlapping(c) == false) {
+          return nullptr;
+        }
       }
     }
   }
@@ -528,7 +522,7 @@ Compaction* LevelCompactionPicker::PickCompactionBySize(Version* version,
   }
 
   // store where to start the iteration in the next call to PickCompaction
-  c->input_version_->next_file_to_compact_by_size_[level] = nextIndex;
+  version->next_file_to_compact_by_size_[level] = nextIndex;
 
   return c;
 }
diff --git a/db/compaction_picker.h b/db/compaction_picker.h
index 980c60013..0fe086a18 100644
--- a/db/compaction_picker.h
+++ b/db/compaction_picker.h
@@ -85,7 +85,17 @@ class CompactionPicker {
                 const std::vector<FileMetaData*>& inputs2,
                 InternalKey* smallest, InternalKey* largest);
 
-  void ExpandWhileOverlapping(Compaction* c);
+  // Add more files to the inputs on "level" to make sure that
+  // no newer version of a key is compacted to "level+1" while leaving an older
+  // version in a "level". Otherwise, any Get() will search "level" first,
+  // and will likely return an old/stale value for the key, since it always
+  // searches in increasing order of level to find the value. This could
+  // also scramble the order of merge operands. This function should be
+  // called any time a new Compaction is created, and its inputs_[0] are
+  // populated.
+  //
+  // Will return false if it is impossible to apply this compaction.
+  bool ExpandWhileOverlapping(Compaction* c);
 
   uint64_t ExpandedCompactionByteSizeLimit(int level);
 
diff --git a/db/db_impl.cc b/db/db_impl.cc
index 57565996a..4149a71bd 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -3202,7 +3202,7 @@ void DBImpl::BuildBatchGroup(Writer** last_writer,
 // The goal of this formula is to gradually increase the rate at which writes
 // are slowed. We also tried linear delay (r * 1000), but it seemed to do
 // slightly worse. There is no other particular reason for choosing quadratic.
-uint64_t DBImpl::SlowdownAmount(int n, int top, int bottom) {
+uint64_t DBImpl::SlowdownAmount(int n, double bottom, double top) {
   uint64_t delay;
   if (n >= top) {
     delay = 1000;
@@ -3214,10 +3214,10 @@ uint64_t DBImpl::SlowdownAmount(int n, int top, int bottom) {
     // If we are here, we know that:
     //   level0_start_slowdown <= n < level0_slowdown
     // since the previous two conditions are false.
-    float how_much =
-      (float) (n - bottom) /
+    double how_much =
+      (double) (n - bottom) /
               (top - bottom);
-    delay = how_much * how_much * 1000;
+    delay = std::max(how_much * how_much * 1000, 100.0);
   }
   assert(delay <= 1000);
   return delay;
diff --git a/db/db_impl.h b/db/db_impl.h
index c43f720b6..eac242593 100644
--- a/db/db_impl.h
+++ b/db/db_impl.h
@@ -293,7 +293,7 @@ class DBImpl : public DB {
   Status WriteLevel0Table(autovector<MemTable*>& mems, VersionEdit* edit,
                                 uint64_t* filenumber);
 
-  uint64_t SlowdownAmount(int n, int top, int bottom);
+  uint64_t SlowdownAmount(int n, double bottom, double top);
   // MakeRoomForWrite will return superversion_to_free through an arugment,
   // which the caller needs to delete. We do it because caller can delete
   // the superversion outside of mutex