diff --git a/CONSTITUTION.md b/CONSTITUTION.md
index 6dc3068..3b26577 100644
--- a/CONSTITUTION.md
+++ b/CONSTITUTION.md
@@ -2,7 +2,7 @@
 
 > 本文件定義專案開發的核心準則與不可違反的規範
 > **建立日期**: 2026-01-12
-> **當前版本**: V10.54 (Vendor management query service extraction)
+> **當前版本**: V10.55 (Cache dashboard competitor decision overview)
 > **最後更新**: 2026-05-01
 
 ---
diff --git a/app.py b/app.py
index a4ce81d..0535b0a 100644
--- a/app.py
+++ b/app.py
@@ -95,8 +95,8 @@ except Exception as e:
     sys_log.error(f"無法檢測磁碟空間: {e}")
 
 # 🚩 系統版本定義 (備份與顯示用)
-# 🚩 2026-05-01 V10.54: Vendor management query service extraction
-SYSTEM_VERSION = "V10.54"
+# 🚩 2026-05-01 V10.55: Cache dashboard competitor decision overview
+SYSTEM_VERSION = "V10.55"
 
 # ==========================================
 # 🔒 SQL Injection 防護函數
diff --git a/config.py b/config.py
index 6624dfa..48e8fe5 100644
--- a/config.py
+++ b/config.py
@@ -254,7 +254,7 @@ YOUTUBE_API_KEY = os.getenv('YOUTUBE_API_KEY', '')
 # ==========================================
 # 系統版本與路徑
 # ==========================================
-SYSTEM_VERSION = "V10.54"
+SYSTEM_VERSION = "V10.55"
 LOG_FILE_PATH = os.path.join(BASE_DIR, 'logs/system.log')
 public_url = PUBLIC_URL  # 用於模板顯示
 
diff --git a/routes/dashboard_routes.py b/routes/dashboard_routes.py
index 2afc5eb..5324cf2 100644
--- a/routes/dashboard_routes.py
+++ b/routes/dashboard_routes.py
@@ -172,6 +172,15 @@ def _dashboard_decision_row(row, tone):
 
 def _load_competitor_decision_overview(session):
     """讀取商品看板第一屏使用的 PChome 比價決策摘要。全部來自正式 DB。"""
+    cache_key = 'competitor_decision_overview'
+    cache_ts_key = 'competitor_decision_overview_timestamp'
+    cached = _DASHBOARD_DATA_CACHE.get(cache_key)
+    cached_ts = _DASHBOARD_DATA_CACHE.get(cache_ts_key)
+    if cached and cached_ts:
+        age = time.time() - cached_ts
+        if age < min(_DASHBOARD_CACHE_TTL, 300):
+            return cached
+
     default = {
         'total_active': 0,
         'matched_count': 0,
@@ -369,6 +378,8 @@ def _load_competitor_decision_overview(session):
             }
             for row in session.execute(pending_sql).mappings().all()
         ]
+        _DASHBOARD_DATA_CACHE[cache_key] = overview
+        _DASHBOARD_DATA_CACHE[cache_ts_key] = time.time()
         return overview
     except Exception as exc:
         sys_log.warning(f"[Dashboard] PChome 比價決策摘要讀取略過: {exc}")
@@ -376,6 +387,8 @@ def _load_competitor_decision_overview(session):
             session.rollback()
         except Exception:
             pass
+        _DASHBOARD_DATA_CACHE[cache_key] = default
+        _DASHBOARD_DATA_CACHE[cache_ts_key] = time.time()
         return default