diff --git a/backend/db.py b/backend/db.py
index 8db513c..9a6f5f6 100644
--- a/backend/db.py
+++ b/backend/db.py
@@ -14,6 +14,7 @@ MariaDB automatically. Upserts must use backend-specific SQL (see services).
 """
 import os
 import sqlite3
+import time
 import threading
 import queue
 import datetime
@@ -511,8 +512,35 @@ def _statements(schema):
             yield stmt
 
 
+# How long to keep waiting for the database at startup.
+#
+# On a NAS reboot the app and MariaDB come up together and the app usually
+# wins the race. Without this it raised, gunicorn reported "Worker failed to
+# boot", the master shut down — and when MariaDB appeared seconds later there
+# was nothing left running to notice. The site stayed down until someone
+# restarted it by hand.
+INIT_RETRY_SECONDS = int(os.environ.get("DB_INIT_RETRY_SECONDS") or 120)
+INIT_RETRY_INTERVAL = 3
+
+
 def init_db():
-    conn = _connect()
+    deadline = time.monotonic() + INIT_RETRY_SECONDS
+    attempt = 0
+    while True:
+        attempt += 1
+        try:
+            conn = _connect()
+            break
+        except Exception as e:  # noqa: BLE001 - any connection failure is worth retrying
+            if time.monotonic() >= deadline:
+                raise
+            if attempt == 1:
+                print(f"[db] 数据库还没准备好，重试中：{e}")
+            time.sleep(INIT_RETRY_INTERVAL)
+
+    if attempt > 1:
+        print(f"[db] 第 {attempt} 次尝试后连上数据库")
+
     try:
         cur = conn.cursor()
         for stmt in _statements(SCHEMA):