diff --git a/contest/contest/tasks.py b/contest/contest/tasks.py
index c753582..5e56544 100644
--- a/contest/contest/tasks.py
+++ b/contest/contest/tasks.py
@@ -1,6 +1,9 @@
-import logging
+"""celery 任务"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
 
-import redis
 from celery import shared_task
 from django.core.cache import cache
 from django.shortcuts import get_object_or_404
@@ -10,59 +13,50 @@
 # 导致运行的时候如果直接import contest.quiz.models会找不到
 # 所以就直接默认已经在contest路径里开始索引，因此lint会报错
 # 但是实际上是可以运行的，忽略Lint报错即可
-from quiz.models import (
-    Choice,
-    DraftAnswer,
-    DraftResponse,
-)
+from quiz.models import Choice, DraftAnswer, DraftResponse
 
-# Get an instance of a logger
-logger = logging.getLogger("django")
+if TYPE_CHECKING:
+    from typing import Generator
 
 
 @shared_task
 def auto_save_redis_to_database() -> None:
-    # 获取 Redis 连接
-    r = redis.Redis(host="127.0.0.1", port=6379, db=1)
-    # 使用 scan_iter 获取所有键
-    keys = r.scan_iter("*_ddl")
-    if keys is None:
-        return
-    for key in keys:
-        ddl_key = key.decode("utf-8")[3:]
-        ddl = cache.get(ddl_key)
-        now = timezone.now()
-        if ddl is not None:
-            if ddl < now:
-                try:
-                    draft_response = DraftResponse.objects.get(id=int(ddl_key[:-4]))
-                    cache_key = f"{ddl_key[:-4]}_json"
-                    # # 从 Redis 获取现有的答案缓存
-                    cached_answers = cache.get(cache_key, {})
-
-                    if cached_answers is not None:  # 防止未提交的是白卷
-                        for question_id, choice_id in cached_answers.items():
-                            # Filter out tokens
-                            if not question_id.startswith("question-"):
-                                continue
-
-                            if not isinstance(choice_id, str) or not choice_id.startswith(
-                                "choice-"
-                            ):
-                                return
-
-                            answer: DraftAnswer = get_object_or_404(
-                                draft_response.answer_set,
-                                question_id=int(question_id.removeprefix("question-")),
-                            )
-
-                            answer.choice = get_object_or_404(
-                                Choice.objects,
-                                pk=int(choice_id.removeprefix("choice-")),
-                                question=answer.question,
-                            )
-
-                            answer.save()
+    """提交 Redis 缓存中过期的答卷草稿"""
+    scanner: Generator[str, None, None] = cache.iter_keys("*_ddl")  # type: ignore[attr-defined]
+    # `iter_keys`由 django-redis 提供，django 本身没有
+    for ddl_key in scanner:
+        pk = ddl_key.removesuffix("_ddl")
+        ddl = cache.get(pk)
+        if ddl is not None and ddl < timezone.now():
+            try:
+                draft_response = DraftResponse.objects.get(pk=pk)
+                cached_answers = cache.get(f"{pk}_json", {})
+
+                # 同步 Redis 缓存到数据库
+                # 若未作答，可能 Redis 中无记录，但数据库中仍有
+                if cached_answers is not None:
+                    for question_id, choice_id in cached_answers.items():
+                        # Filter out tokens
+                        if not question_id.startswith("question-"):
+                            continue
+
+                        if not isinstance(choice_id, str) or not choice_id.startswith(
+                            "choice-"
+                        ):
+                            return
+
+                        answer: DraftAnswer = get_object_or_404(
+                            draft_response.answer_set,
+                            question_id=int(question_id.removeprefix("question-")),
+                        )
+
+                        answer.choice = get_object_or_404(
+                            Choice.objects,
+                            pk=int(choice_id.removeprefix("choice-")),
+                            question=answer.question,
+                        )
+
+                        answer.save()
 
                     # 1. Convert from draft
                     response, answers = draft_response.finalize(submit_at=timezone.now())
@@ -72,9 +66,11 @@ def auto_save_redis_to_database() -> None:
                     response.answer_set.bulk_create(answers)
                     draft_response.delete()
 
-                except DraftResponse.DoesNotExist as e:
-                    print("here is tasks.py 74 line")
-                    print(e)
+            except DraftResponse.DoesNotExist as e:
+                print("here is tasks.py 74 line")
+                print(e)
 
-                r.delete(key)
-                r.delete(":1:" + ddl_key[:-4] + "_json")
+            # 即使`DraftResponse.DoesNotExist`，也应尝试删除 Redis 中的记录
+            # 因为可能是 Django 正常处理过了
+            cache.delete(f"{pk}_ddl")
+            cache.delete(f"{pk}_json")