diff --git a/tddb/td/db/BinlogKeyValue.h b/tddb/td/db/BinlogKeyValue.h
index 6b6e68422..629795cc9 100644
--- a/tddb/td/db/BinlogKeyValue.h
+++ b/tddb/td/db/BinlogKeyValue.h
@@ -14,7 +14,7 @@
 #include "td/utils/algorithm.h"
 #include "td/utils/buffer.h"
 #include "td/utils/common.h"
-#include "td/utils/HashTableUtils.h"
+#include "td/utils/FlatHashMap.h"
 #include "td/utils/logging.h"
 #include "td/utils/misc.h"
 #include "td/utils/port/RwMutex.h"
@@ -26,7 +26,6 @@
 #include "td/utils/tl_storers.h"
 
 #include <memory>
-#include <unordered_map>
 #include <utility>
 
 namespace td {
@@ -83,6 +82,10 @@ class BinlogKeyValue final : public KeyValueSyncInterface {
         [&](const BinlogEvent &binlog_event) {
           Event event;
           event.parse(TlParser(binlog_event.get_data()));
+          if (event.key.empty()) {
+            LOG(ERROR) << "Have event with empty key";
+            return;
+          }
           map_.emplace(event.key.str(), std::make_pair(event.value.str(), binlog_event.id_));
         },
         std::move(db_key), DbKey::empty(), scheduler_id));
@@ -104,6 +107,10 @@ class BinlogKeyValue final : public KeyValueSyncInterface {
   void external_init_handle(const BinlogEvent &binlog_event) {
     Event event;
     event.parse(TlParser(binlog_event.get_data()));
+    if (event.key.empty()) {
+      LOG(ERROR) << "Have external event with empty key";
+      return;
+    }
     map_.emplace(event.key.str(), std::make_pair(event.value.str(), binlog_event.id_));
   }
 
@@ -121,6 +128,7 @@ class BinlogKeyValue final : public KeyValueSyncInterface {
   SeqNo set(string key, string value) final {
     auto lock = rw_mutex_.lock_write().move_as_ok();
     uint64 old_event_id = 0;
+    CHECK(!key.empty());
     auto it_ok = map_.emplace(key, std::make_pair(value, 0));
     if (!it_ok.second) {
       if (it_ok.first->second.first == value) {
@@ -210,9 +218,9 @@ class BinlogKeyValue final : public KeyValueSyncInterface {
     binlog_->lazy_sync(std::move(promise));
   }
 
-  std::unordered_map<string, string, Hash<string>> prefix_get(Slice prefix) final {
+  FlatHashMap<string, string> prefix_get(Slice prefix) final {
     auto lock = rw_mutex_.lock_write().move_as_ok();
-    std::unordered_map<string, string, Hash<string>> res;
+    FlatHashMap<string, string> res;
     for (const auto &kv : map_) {
       if (begins_with(kv.first, prefix)) {
         res.emplace(kv.first.substr(prefix.size()), kv.second.first);
@@ -221,9 +229,9 @@ class BinlogKeyValue final : public KeyValueSyncInterface {
     return res;
   }
 
-  std::unordered_map<string, string, Hash<string>> get_all() final {
+  FlatHashMap<string, string> get_all() final {
     auto lock = rw_mutex_.lock_write().move_as_ok();
-    std::unordered_map<string, string, Hash<string>> res;
+    FlatHashMap<string, string> res;
     for (const auto &kv : map_) {
       res.emplace(kv.first, kv.second.first);
     }
@@ -248,6 +256,7 @@ class BinlogKeyValue final : public KeyValueSyncInterface {
       seq_no++;
     }
   }
+
   template <class T>
   friend class BinlogKeyValue;
 
@@ -256,7 +265,7 @@ class BinlogKeyValue final : public KeyValueSyncInterface {
   }
 
  private:
-  std::unordered_map<string, std::pair<string, uint64>, Hash<string>> map_;
+  FlatHashMap<string, std::pair<string, uint64>> map_;
   std::shared_ptr<BinlogT> binlog_;
   RwMutex rw_mutex_;
   int32 magic_ = MAGIC;
diff --git a/tddb/td/db/KeyValueSyncInterface.h b/tddb/td/db/KeyValueSyncInterface.h
index 111882fb2..09515974f 100644
--- a/tddb/td/db/KeyValueSyncInterface.h
+++ b/tddb/td/db/KeyValueSyncInterface.h
@@ -7,12 +7,10 @@
 #pragma once
 
 #include "td/utils/common.h"
-#include "td/utils/HashTableUtils.h"
+#include "td/utils/FlatHashMap.h"
 #include "td/utils/Promise.h"
 #include "td/utils/Slice.h"
 
-#include <unordered_map>
-
 namespace td {
 
 class KeyValueSyncInterface {
@@ -34,9 +32,9 @@ class KeyValueSyncInterface {
 
   virtual string get(const string &key) = 0;
 
-  virtual std::unordered_map<string, string, Hash<string>> prefix_get(Slice prefix) = 0;
+  virtual FlatHashMap<string, string> prefix_get(Slice prefix) = 0;
 
-  virtual std::unordered_map<string, string, Hash<string>> get_all() = 0;
+  virtual FlatHashMap<string, string> get_all() = 0;
 
   virtual SeqNo erase(const string &key) = 0;