diff --git a/common/expired_dict.py b/common/expired_dict.py
index ccf16c7..ab449ee 100644
--- a/common/expired_dict.py
+++ b/common/expired_dict.py
@@ -1,23 +1,50 @@
-from datetime import datetime, timedelta
+import time
+from collections import OrderedDict
 
-class ExpiredDict(dict):
+
+class ExpiredDict(OrderedDict):
     def __init__(self, expires_in_seconds):
         super().__init__()
+        # 存储键值对的生存时间
         self.expires_in_seconds = expires_in_seconds
+        # 获取当前时间的函数
+        self.now = time.monotonic
 
     def __getitem__(self, key):
-        value, expiry_time = super().__getitem__(key)
-        if datetime.now() > expiry_time:
+        # 检查键是否存在
+        if key not in self:
+            raise KeyError(key)
+        # 获取值和过期时间
+        value, expiry_time = self[key]
+        # 如果过期时间早于当前时间，删除该键值对并引发 KeyError
+        if expiry_time is not None and self.now() > expiry_time:
             del self[key]
-            raise KeyError("expired {}".format(key))
-        self.__setitem__(key, value)
+            raise KeyError(key)
+        # 如果存活时间不为 None，更新该键值对的过期时间
+        if self.expires_in_seconds is not None:
+            self[key] = value, self.now() + self.expires_in_seconds
+        # 删除过期的键值对
+        self._delete_expired_items()
+        # 返回值
         return value
 
     def __setitem__(self, key, value):
-        expiry_time = datetime.now() + timedelta(seconds=self.expires_in_seconds)
-        super().__setitem__(key, (value, expiry_time))
+        # 如果存活时间不为 None，设置该键值对的过期时间
+        if self.expires_in_seconds is not None:
+            self[key] = value, self.now() + self.expires_in_seconds
+        else:
+            self[key] = value, None
+        # 删除过期的键值对
+        self._delete_expired_items()
+
     def get(self, key, default=None):
         try:
             return self[key]
         except KeyError:
-            return default
\ No newline at end of file
+            return default
+
+    def _delete_expired_items(self):
+        # 遍历所有键值对，删除过期的键值对
+        for key, (value, expiry_time) in list(self.items()):
+            if expiry_time is not None and self.now() > expiry_time:
+                del self[key]