diff --git a/achievement/checker.py b/achievement/checker.py
index 7ce0c5e..d98882c 100644
--- a/achievement/checker.py
+++ b/achievement/checker.py
@@ -15,11 +15,6 @@ from achievement.models import Achievement, Operator, UserAchievement, UserStat
 logger = logging.getLogger(__name__)
 
 
-def get_or_create_stat(user):
-    stat, _ = UserStat.objects.get_or_create(user=user)
-    return stat
-
-
 def evaluate(user, metrics, only_metrics=None):
     """返回该用户应解锁但尚未解锁的成就列表。"""
     unlocked_ids = set(UserAchievement.objects.filter(user=user).values_list("achievement_id", flat=True))
diff --git a/problem/serializers.py b/problem/serializers.py
index e3a4dde..55c6cb6 100644
--- a/problem/serializers.py
+++ b/problem/serializers.py
@@ -253,12 +253,6 @@ class TestCaseScoreSerializer(serializers.Serializer):
     output_name = serializers.CharField(max_length=32)
 
 
-class TemplateSerializer(serializers.Serializer):
-    prepend = serializers.CharField()
-    template = serializers.CharField()
-    append = serializers.CharField()
-
-
 class AnswerSerializer(serializers.Serializer):
     code = serializers.CharField()
     language = LanguageNameChoiceField()
diff --git a/problem/utils.py b/problem/utils.py
index 92a2a06..8c42449 100644
--- a/problem/utils.py
+++ b/problem/utils.py
@@ -29,11 +29,6 @@ def parse_problem_template(template_str):
     return {"prepend": prepend[0] if prepend else "", "template": template[0] if template else "", "append": append[0] if append else ""}
 
 
-@lru_cache(maxsize=100)
-def build_problem_template(prepend, template, append):
-    return TEMPLATE_BASE.format(prepend, template, append)
-
-
 def generate_sql_display(test_case_id, answers, sql_config):
     """SQL 题：用测试点1的初始化脚本 + 标准答案生成题目页展示数据。
 
diff --git a/utils/async_helpers.py b/utils/async_helpers.py
index 056cfa1..d61c790 100644
--- a/utils/async_helpers.py
+++ b/utils/async_helpers.py
@@ -8,6 +8,3 @@ async def async_cache_get(key, default=None):
 async def async_cache_set(key, value, timeout=None):
     return await cache.aset(key, value, timeout)
 
-
-async def async_cache_delete(key):
-    return await cache.adelete(key)
diff --git a/utils/shortcuts.py b/utils/shortcuts.py
index 3efa222..39a7de7 100644
--- a/utils/shortcuts.py
+++ b/utils/shortcuts.py
@@ -35,20 +35,6 @@ def rand_str(length=32, type="lower_hex"):
         return random.choice("123456789") + get_random_string(length - 1, allowed_chars="0123456789")
 
 
-def build_query_string(kv_data, ignore_none=True):
-    # {"a": 1, "b": "test"} -> "?a=1&b=test"
-    query_string = ""
-    for k, v in kv_data.items():
-        if ignore_none is True and kv_data[k] is None:
-            continue
-        if query_string != "":
-            query_string += "&"
-        else:
-            query_string = "?"
-        query_string += k + "=" + str(v)
-    return query_string
-
-
 def strip_class_prefix(username, class_name):
     """
     去掉用户名里的 ks<班级号> 前缀，得到学生本人那一段。
diff --git a/utils/tasks.py b/utils/tasks.py
deleted file mode 100644
index d431157..0000000
--- a/utils/tasks.py
+++ /dev/null
@@ -1,14 +0,0 @@
-import os
-
-import dramatiq
-
-from utils.shortcuts import DRAMATIQ_WORKER_ARGS
-
-
-@dramatiq.actor(**DRAMATIQ_WORKER_ARGS())
-def delete_files(*args):
-    for item in args:
-        try:
-            os.remove(item)
-        except Exception:
-            pass