diff --git a/td/telegram/ConfigShared.h b/td/telegram/ConfigShared.h
index c49d8b4c0..a9b8e89b1 100644
--- a/td/telegram/ConfigShared.h
+++ b/td/telegram/ConfigShared.h
@@ -25,7 +25,7 @@ class ConfigShared {
     Callback(const Callback &) = delete;
     Callback &operator=(const Callback &) = delete;
     virtual ~Callback() = default;
-    virtual void on_option_updated(const string &name, const string &value) = 0;
+    virtual void on_option_updated(const string &name, const string &value) const = 0;
   };
 
   ConfigShared(BinlogPmcPtr config_pmc, unique_ptr<Callback> callback);
diff --git a/td/telegram/Game.cpp b/td/telegram/Game.cpp
index ce17046c5..f065ca073 100644
--- a/td/telegram/Game.cpp
+++ b/td/telegram/Game.cpp
@@ -91,7 +91,7 @@ const FormattedText &Game::get_message_text() const {
   return text_;
 }
 
-tl_object_ptr<td_api::game> Game::get_game_object(const Td *td) const {
+tl_object_ptr<td_api::game> Game::get_game_object(Td *td) const {
   return make_tl_object<td_api::game>(
       id_, short_name_, title_, get_formatted_text_object(text_), description_,
       get_photo_object(td->file_manager_.get(), &photo_),
diff --git a/td/telegram/Game.h b/td/telegram/Game.h
index a9b2a3204..98eed6642 100644
--- a/td/telegram/Game.h
+++ b/td/telegram/Game.h
@@ -59,7 +59,7 @@ class Game {
 
   const FormattedText &get_message_text() const;
 
-  tl_object_ptr<td_api::game> get_game_object(const Td *td) const;
+  tl_object_ptr<td_api::game> get_game_object(Td *td) const;
 
   tl_object_ptr<telegram_api::inputMediaGame> get_input_media_game(const Td *td) const;
 
diff --git a/td/telegram/MessagesManager.cpp b/td/telegram/MessagesManager.cpp
index fac5d7a98..c53ad484d 100644
--- a/td/telegram/MessagesManager.cpp
+++ b/td/telegram/MessagesManager.cpp
@@ -12755,7 +12755,7 @@ Status MessagesManager::delete_dialog_reply_markup(DialogId dialog_id, MessageId
     return Status::OK();
   }
 
-  const Message *message = get_message_force(d, message_id);
+  Message *message = get_message_force(d, message_id);
   CHECK(message != nullptr);
   CHECK(message->reply_markup != nullptr);
 
@@ -14140,7 +14140,7 @@ tl_object_ptr<td_api::messages> MessagesManager::get_dialog_history(DialogId dia
     if (*p == nullptr) {
       // there is no gap if from_message_id is less than first message in the dialog
       if (left_tries == 0 && d->messages != nullptr && offset < 0) {
-        Message *cur = d->messages.get();
+        const Message *cur = d->messages.get();
         while (cur->left != nullptr) {
           cur = cur->left.get();
         }
diff --git a/td/telegram/MessagesManager.h b/td/telegram/MessagesManager.h
index faa747e45..df2132eb0 100644
--- a/td/telegram/MessagesManager.h
+++ b/td/telegram/MessagesManager.h
@@ -1585,7 +1585,7 @@ class MessagesManager : public Actor {
     unique_ptr<Message> left;
     unique_ptr<Message> right;
 
-    int32 last_access_date = 0;
+    mutable int32 last_access_date = 0;
 
     uint64 send_message_logevent_id = 0;
 
diff --git a/td/telegram/Td.cpp b/td/telegram/Td.cpp
index 7c8e36b5d..0c6fa6103 100644
--- a/td/telegram/Td.cpp
+++ b/td/telegram/Td.cpp
@@ -4053,7 +4053,7 @@ Status Td::init(DbKey key) {
   VLOG(td_init) << "Create ConfigManager and ConfigShared";
   class ConfigSharedCallback : public ConfigShared::Callback {
    public:
-    void on_option_updated(const string &name, const string &value) override {
+    void on_option_updated(const string &name, const string &value) const override {
       send_closure(G()->td(), &Td::on_config_option_updated, name);
     }
   };
diff --git a/td/telegram/files/FileGenerateManager.cpp b/td/telegram/files/FileGenerateManager.cpp
index 6240c435f..d04930f60 100644
--- a/td/telegram/files/FileGenerateManager.cpp
+++ b/td/telegram/files/FileGenerateManager.cpp
@@ -88,17 +88,18 @@ class FileDownloadGenerateActor : public FileGenerateActor {
   }
 
   void on_download_ok() {
-    send_lambda(G()->file_manager(), [file_type = file_type_, file_id = file_id_, callback = std::move(callback_)] {
-      auto file_view = G()->td().get_actor_unsafe()->file_manager_->get_file_view(file_id);
-      if (file_view.has_local_location()) {
-        auto location = file_view.local_location();
-        location.file_type_ = file_type;
-        callback->on_ok(location);
-      } else {
-        LOG(ERROR) << "Expected to have local location";
-        callback->on_error(Status::Error(500, "Unknown"));
-      }
-    });
+    send_lambda(G()->file_manager(),
+                [file_type = file_type_, file_id = file_id_, callback = std::move(callback_)]() mutable {
+                  auto file_view = G()->td().get_actor_unsafe()->file_manager_->get_file_view(file_id);
+                  if (file_view.has_local_location()) {
+                    auto location = file_view.local_location();
+                    location.file_type_ = file_type;
+                    callback->on_ok(location);
+                  } else {
+                    LOG(ERROR) << "Expected to have local location";
+                    callback->on_error(Status::Error(500, "Unknown"));
+                  }
+                });
     stop();
   }
   void on_download_error(Status error) {
diff --git a/td/tl/TlObject.h b/td/tl/TlObject.h
index eaeecae0e..c93066fba 100644
--- a/td/tl/TlObject.h
+++ b/td/tl/TlObject.h
@@ -175,6 +175,7 @@ template <class T>
 bool operator!=(const unique_ptr<T> &p, std::nullptr_t) {
   return static_cast<bool>(p);
 }
+
 }  // namespace tl
 template <class Type>
 using tl_object_ptr = tl::unique_ptr<Type>;
diff --git a/tdutils/td/utils/unique_ptr.h b/tdutils/td/utils/unique_ptr.h
index ee6e25e30..959dedf55 100644
--- a/tdutils/td/utils/unique_ptr.h
+++ b/tdutils/td/utils/unique_ptr.h
@@ -12,8 +12,10 @@
 
 namespace td {
 
+// const-correct and compiler-friendly (g++ RAM and CPU usage 10 times less than for std::unique_ptr)
+// replacement for std::unique_ptr
 template <class T>
-class unique_ptr {
+class unique_ptr final {
  public:
   using pointer = T *;
   using element_type = T;
@@ -52,13 +54,22 @@ class unique_ptr {
     ptr_ = nullptr;
     return res;
   }
-  T *get() const noexcept {
+  T *get() noexcept {
     return ptr_;
   }
-  T *operator->() const noexcept {
+  const T *get() const noexcept {
     return ptr_;
   }
-  T &operator*() const noexcept {
+  T *operator->() noexcept {
+    return ptr_;
+  }
+  const T *operator->() const noexcept {
+    return ptr_;
+  }
+  T &operator*() noexcept {
+    return *ptr_;
+  }
+  const T &operator*() const noexcept {
     return *ptr_;
   }
   explicit operator bool() const noexcept {