diff --git a/services/cache_service.py b/services/cache_service.py
index d57a7b1..9b5b91a 100644
--- a/services/cache_service.py
+++ b/services/cache_service.py
@@ -1,8 +1,10 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 """
-快取服務模組
-集中管理所有快取變數和相關操作
+Legacy cache compatibility shim.
+
+Sales/dashboard cache state lives in services.cache_manager. This module keeps
+older imports working and only owns growth-analysis and slow-query helpers.
 """
 
 from datetime import datetime, timezone, timedelta