diff --git a/td/telegram/PollManager.cpp b/td/telegram/PollManager.cpp
index 2562b7e83..4d969eb72 100644
--- a/td/telegram/PollManager.cpp
+++ b/td/telegram/PollManager.cpp
@@ -329,18 +329,16 @@ void PollManager::notify_on_poll_update(PollId poll_id) {
     return;
   }
 
-  auto server_it = server_poll_messages_.find(poll_id);
-  if (server_it != server_poll_messages_.end()) {
-    for (const auto &full_message_id : server_it->second) {
+  if (server_poll_messages_.count(poll_id) > 0) {
+    server_poll_messages_[poll_id].foreach([&](const FullMessageId &full_message_id) {
       td_->messages_manager_->on_external_update_message_content(full_message_id);
-    }
+    });
   }
 
-  auto other_it = other_poll_messages_.find(poll_id);
-  if (other_it != other_poll_messages_.end()) {
-    for (const auto &full_message_id : other_it->second) {
+  if (other_poll_messages_.count(poll_id) > 0) {
+    other_poll_messages_[poll_id].foreach([&](const FullMessageId &full_message_id) {
       td_->messages_manager_->on_external_update_message_content(full_message_id);
-    }
+    });
   }
 }
 
@@ -647,14 +645,12 @@ PollId PollManager::create_poll(string &&question, vector<string> &&options, boo
 void PollManager::register_poll(PollId poll_id, FullMessageId full_message_id, const char *source) {
   CHECK(have_poll(poll_id));
   if (full_message_id.get_message_id().is_scheduled() || !full_message_id.get_message_id().is_server()) {
-    bool is_inserted = other_poll_messages_[poll_id].insert(full_message_id).second;
-    LOG_CHECK(is_inserted) << source << ' ' << poll_id << ' ' << full_message_id;
+    other_poll_messages_[poll_id].insert(full_message_id);
     unload_poll_timeout_.cancel_timeout(poll_id.get());
     return;
   }
   LOG(INFO) << "Register " << poll_id << " from " << full_message_id << " from " << source;
-  bool is_inserted = server_poll_messages_[poll_id].insert(full_message_id).second;
-  LOG_CHECK(is_inserted) << source << ' ' << poll_id << ' ' << full_message_id;
+  server_poll_messages_[poll_id].insert(full_message_id);
   auto poll = get_poll(poll_id);
   CHECK(poll != nullptr);
   if (!td_->auth_manager_->is_bot() && !is_local_poll_id(poll_id) &&
@@ -1265,12 +1261,11 @@ void PollManager::on_update_poll_timeout(PollId poll_id) {
     return;
   }
 
-  auto it = server_poll_messages_.find(poll_id);
-  if (it == server_poll_messages_.end()) {
+  if (server_poll_messages_.count(poll_id) == 0) {
     return;
   }
 
-  auto full_message_id = *it->second.begin();
+  auto full_message_id = server_poll_messages_[poll_id].get_random();
   LOG(INFO) << "Fetching results of " << poll_id << " from " << full_message_id;
   auto query_promise = PromiseCreator::lambda([poll_id, generation = current_generation_, actor_id = actor_id(this)](
                                                   Result<tl_object_ptr<telegram_api::Updates>> &&result) {
@@ -1379,14 +1374,13 @@ void PollManager::on_online() {
     return;
   }
 
-  for (auto &it : server_poll_messages_) {
-    auto poll_id = it.first;
+  server_poll_messages_.foreach([&](const PollId &poll_id, WaitFreeHashSet<FullMessageId, FullMessageIdHash> &) {
     if (update_poll_timeout_.has_timeout(poll_id.get())) {
       auto timeout = Random::fast(3, 30);
       LOG(INFO) << "Schedule updating of " << poll_id << " in " << timeout;
       update_poll_timeout_.set_timeout_in(poll_id.get(), timeout);
     }
-  }
+  });
 }
 
 PollId PollManager::dup_poll(PollId poll_id) {
diff --git a/td/telegram/PollManager.h b/td/telegram/PollManager.h
index 9b318bec6..fb38dfaac 100644
--- a/td/telegram/PollManager.h
+++ b/td/telegram/PollManager.h
@@ -25,6 +25,7 @@
 #include "td/utils/Promise.h"
 #include "td/utils/Status.h"
 #include "td/utils/WaitFreeHashMap.h"
+#include "td/utils/WaitFreeHashSet.h"
 
 #include <utility>
 
@@ -227,8 +228,8 @@ class PollManager final : public Actor {
   ActorShared<> parent_;
   WaitFreeHashMap<PollId, unique_ptr<Poll>, PollIdHash> polls_;
 
-  FlatHashMap<PollId, FlatHashSet<FullMessageId, FullMessageIdHash>, PollIdHash> server_poll_messages_;
-  FlatHashMap<PollId, FlatHashSet<FullMessageId, FullMessageIdHash>, PollIdHash> other_poll_messages_;
+  WaitFreeHashMap<PollId, WaitFreeHashSet<FullMessageId, FullMessageIdHash>, PollIdHash> server_poll_messages_;
+  WaitFreeHashMap<PollId, WaitFreeHashSet<FullMessageId, FullMessageIdHash>, PollIdHash> other_poll_messages_;
 
   struct PendingPollAnswer {
     vector<string> options_;
diff --git a/tdutils/td/utils/WaitFreeHashSet.h b/tdutils/td/utils/WaitFreeHashSet.h
index 6573a6d80..c7e6ad808 100644
--- a/tdutils/td/utils/WaitFreeHashSet.h
+++ b/tdutils/td/utils/WaitFreeHashSet.h
@@ -96,6 +96,22 @@ class WaitFreeHashSet {
     }
   }
 
+  KeyT get_random() const {
+    if (wait_free_storage_ != nullptr) {
+      for (size_t i = 0; i < MAX_STORAGE_COUNT; i++) {
+        if (!wait_free_storage_->sets_[i].empty()) {
+          return wait_free_storage_->sets_[i].get_random();
+        }
+      }
+      // no need to explicitly return KeyT()
+    }
+
+    if (default_set_.empty()) {
+      return KeyT();
+    }
+    return *default_set_.begin();
+  }
+
   size_t calc_size() const {
     if (wait_free_storage_ == nullptr) {
       return default_set_.size();