diff --git a/td/telegram/ConfigManager.cpp b/td/telegram/ConfigManager.cpp
index 5002de8c2..4d70a3c14 100644
--- a/td/telegram/ConfigManager.cpp
+++ b/td/telegram/ConfigManager.cpp
@@ -420,7 +420,7 @@ static ActorOwn<> get_full_config(DcOption option, Promise<tl_object_ptr<telegra
     void on_server_salt_updated(std::vector<mtproto::ServerSalt> server_salts) final {
       // nop
     }
-    void on_update(BufferSlice &&update) final {
+    void on_update(BufferSlice &&update, uint64 auth_key_id) final {
       // nop
     }
     void on_result(NetQueryPtr net_query) final {
@@ -1356,7 +1356,7 @@ void ConfigManager::process_config(tl_object_ptr<telegram_api::config> config) {
   }
   if (is_from_main_dc) {
     options.set_option_integer("webfile_dc_id", config->webfile_dc_id_);
-    if ((config->flags_ & telegram_api::config::TMP_SESSIONS_MASK) != 0) {
+    if ((config->flags_ & telegram_api::config::TMP_SESSIONS_MASK) != 0 && config->tmp_sessions_ > 1) {
       options.set_option_integer("session_count", config->tmp_sessions_);
     } else {
       options.set_option_empty("session_count");
diff --git a/td/telegram/Td.cpp b/td/telegram/Td.cpp
index 3d5374d5c..593150328 100644
--- a/td/telegram/Td.cpp
+++ b/td/telegram/Td.cpp
@@ -3064,7 +3064,7 @@ std::shared_ptr<Td::ResultHandler> Td::extract_handler(uint64 id) {
   return result;
 }
 
-void Td::on_update(BufferSlice &&update) {
+void Td::on_update(BufferSlice &&update, uint64 auth_key_id) {
   if (close_flag_ > 1) {
     return;
   }
@@ -3076,6 +3076,7 @@ void Td::on_update(BufferSlice &&update) {
     LOG(ERROR) << "Failed to fetch update: " << parser.get_error() << format::as_hex_dump<4>(update.as_slice());
     updates_manager_->schedule_get_difference("failed to fetch update");
   } else {
+    updates_manager_->on_update_from_auth_key_id(auth_key_id);
     updates_manager_->on_get_updates(std::move(ptr), Promise<Unit>());
     if (auth_manager_->is_bot() && auth_manager_->is_authorized()) {
       alarm_timeout_.set_timeout_in(PING_SERVER_ALARM_ID,
diff --git a/td/telegram/Td.h b/td/telegram/Td.h
index 6c42a7a26..f557081e0 100644
--- a/td/telegram/Td.h
+++ b/td/telegram/Td.h
@@ -118,7 +118,7 @@ class Td final : public Actor {
 
   void schedule_get_promo_data(int32 expires_in);
 
-  void on_update(BufferSlice &&update);
+  void on_update(BufferSlice &&update, uint64 auth_key_id);
 
   void on_result(NetQueryPtr query);
 
diff --git a/td/telegram/UpdatesManager.cpp b/td/telegram/UpdatesManager.cpp
index bc925e6c2..f217cb2de 100644
--- a/td/telegram/UpdatesManager.cpp
+++ b/td/telegram/UpdatesManager.cpp
@@ -303,7 +303,22 @@ void UpdatesManager::fill_gap(void *td, const char *source) {
   auto updates_manager = static_cast<Td *>(td)->updates_manager_.get();
 
   if (source != nullptr && !updates_manager->running_get_difference_) {
-    LOG(WARNING) << "Filling gap in " << source << " by running getDifference";
+    auto auth_key_id = updates_manager->get_most_unused_auth_key_id();
+    uint64 update_count = 0;
+    double active_time = 0.0;
+    double delay_time = 0.0;
+    if (auth_key_id != 0) {
+      auto now = Time::now();
+      auto &info = updates_manager->session_infos_[auth_key_id];
+      update_count = info.update_count;
+      active_time = now - info.first_update_time;
+      delay_time = now - info.last_update_time;
+    }
+
+    LOG(WARNING) << "Filling gap in " << source
+                 << " by running getDifference. Receive no updates from session with auth key " << auth_key_id
+                 << " for " << delay_time << " seconds, active for " << active_time << " seconds and having "
+                 << update_count << " received updates";
   }
 
   updates_manager->get_difference("fill_gap");
@@ -1479,6 +1494,37 @@ void UpdatesManager::init_state() {
   get_difference("init_state");
 }
 
+uint64 UpdatesManager::get_most_unused_auth_key_id() {
+  uint64 min_auth_key_id = 0;
+  double min_time = Time::now();
+  for (auto &it : session_infos_) {
+    if (it.second.last_update_time < min_time) {
+      min_time = it.second.last_update_time;
+      min_auth_key_id = it.first;
+    }
+  }
+  return min_auth_key_id;
+}
+
+void UpdatesManager::on_update_from_auth_key_id(uint64 auth_key_id) {
+  if (auth_key_id == 0) {
+    return;
+  }
+
+  auto &info = session_infos_[auth_key_id];
+  auto now = Time::now();
+  info.last_update_time = now;
+  if (info.update_count++ == 0) {
+    info.first_update_time = now;
+    while (session_infos_.size() >
+           static_cast<size_t>(max(narrow_cast<int32>(G()->get_option_integer("session_count")), 1))) {
+      auto unused_auth_key_id = get_most_unused_auth_key_id();
+      LOG(INFO) << "Delete statistics for auth key " << unused_auth_key_id;
+      session_infos_.erase(unused_auth_key_id);
+    }
+  }
+}
+
 void UpdatesManager::ping_server() {
   if (is_ping_sent_) {
     return;
diff --git a/td/telegram/UpdatesManager.h b/td/telegram/UpdatesManager.h
index 1a8029b97..4b703f4c2 100644
--- a/td/telegram/UpdatesManager.h
+++ b/td/telegram/UpdatesManager.h
@@ -130,6 +130,8 @@ class UpdatesManager final : public Actor {
 
   void schedule_get_difference(const char *source);
 
+  void on_update_from_auth_key_id(uint64 auth_key_id);
+
   void ping_server();
 
   bool running_get_difference() const {
@@ -251,6 +253,13 @@ class UpdatesManager final : public Actor {
   FlatHashMap<int64, TranscribedAudioHandler> pending_audio_transcriptions_;
   MultiTimeout pending_audio_transcription_timeout_{"PendingAudioTranscriptionTimeout"};
 
+  struct SessionInfo {
+    uint64 update_count = 0;
+    double first_update_time = 0.0;
+    double last_update_time = 0.0;
+  };
+  FlatHashMap<uint64, SessionInfo> session_infos_;
+
   void start_up() final;
 
   void tear_down() final;
@@ -365,6 +374,8 @@ class UpdatesManager final : public Actor {
 
   void try_reload_data();
 
+  uint64 get_most_unused_auth_key_id();
+
   static vector<int32> get_update_ids(const telegram_api::Updates *updates_ptr);
 
   static bool have_update_pts_changed(const vector<tl_object_ptr<telegram_api::Update>> &updates);
diff --git a/td/telegram/net/Session.cpp b/td/telegram/net/Session.cpp
index b91ddc344..b3b65a5ee 100644
--- a/td/telegram/net/Session.cpp
+++ b/td/telegram/net/Session.cpp
@@ -704,7 +704,7 @@ void Session::on_session_created(uint64 unique_id, uint64 first_message_id) {
     BufferSlice packet(4);
     as<int32>(packet.as_slice().begin()) = telegram_api::updatesTooLong::ID;
     last_activity_timestamp_ = Time::now();
-    callback_->on_update(std::move(packet));
+    callback_->on_update(std::move(packet), auth_data_.get_auth_key().id());
   }
 
   for (auto it = sent_queries_.begin(); it != sent_queries_.end();) {
@@ -858,7 +858,7 @@ Status Session::on_update(BufferSlice packet) {
     last_success_timestamp_ = Time::now();
   }
   last_activity_timestamp_ = Time::now();
-  callback_->on_update(std::move(packet));
+  callback_->on_update(std::move(packet), auth_data_.get_auth_key().id());
   return Status::OK();
 }
 
diff --git a/td/telegram/net/Session.h b/td/telegram/net/Session.h
index 0895a9263..d56e41eb8 100644
--- a/td/telegram/net/Session.h
+++ b/td/telegram/net/Session.h
@@ -62,7 +62,7 @@ class Session final
                                         Promise<unique_ptr<mtproto::RawConnection>>) = 0;
     virtual void on_tmp_auth_key_updated(mtproto::AuthKey auth_key) = 0;
     virtual void on_server_salt_updated(vector<mtproto::ServerSalt> server_salts) = 0;
-    virtual void on_update(BufferSlice &&update) = 0;
+    virtual void on_update(BufferSlice &&update, uint64 auth_key_id) = 0;
     virtual void on_result(NetQueryPtr net_query) = 0;
   };
 
diff --git a/td/telegram/net/SessionProxy.cpp b/td/telegram/net/SessionProxy.cpp
index c8310b4b6..3e0bde4d9 100644
--- a/td/telegram/net/SessionProxy.cpp
+++ b/td/telegram/net/SessionProxy.cpp
@@ -58,8 +58,8 @@ class SessionCallback final : public Session::Callback {
     send_closure(parent_, &SessionProxy::on_server_salt_updated, std::move(server_salts));
   }
 
-  void on_update(BufferSlice &&update) final {
-    send_closure_later(G()->td(), &Td::on_update, std::move(update));
+  void on_update(BufferSlice &&update, uint64 auth_key_id) final {
+    send_closure_later(G()->td(), &Td::on_update, std::move(update), auth_key_id);
   }
 
   void on_result(NetQueryPtr query) final {