diff --git a/src/state.py b/src/state.py
index 5553095..d758fdd 100644
--- a/src/state.py
+++ b/src/state.py
@@ -20,6 +20,23 @@ _DEFAULT_READMANGA_DOMAINS = [
     "3.readmanga.ru",
 ]
 
+_ALLOWED_FMTS = frozenset({"cbz", "pdf", "epub"})
+
+
+def _now() -> str:
+    return datetime.now(timezone.utc).replace(tzinfo=None).isoformat()
+
+
+def _extract_domain(url: str) -> str:
+    """Извлекает домен без www."""
+    try:
+        domain = urlparse(url).netloc.lower()
+        if domain.startswith("www."):
+            domain = domain[4:]
+        return domain
+    except Exception:
+        return ""
+
 
 class StateDB:
     def __init__(self, db_path: Path = DB_PATH):
@@ -673,21 +690,3 @@ class StateDB:
         self.conn.close()
 
 
-_ALLOWED_FMTS = frozenset({"cbz", "pdf", "epub"})
-
-
-def _now() -> str:
-    return datetime.now(timezone.utc).replace(tzinfo=None).isoformat()
-
-
-def _extract_domain(url: str) -> str:
-    """Извлекает домен без www."""
-    try:
-        domain = urlparse(url).netloc.lower()
-        if domain.startswith("www."):
-            domain = domain[4:]
-        return domain
-    except Exception:
-        return ""
-
-
diff --git a/src/worker.py b/src/worker.py
index 953612e..bfe2ee5 100644
--- a/src/worker.py
+++ b/src/worker.py
@@ -332,15 +332,21 @@ async def check_for_updates(
                 pass
 
     db = StateDB()
+    db_lock = asyncio.Lock()
+
+    async def db_call(fn, *args, **kwargs):
+        async with db_lock:
+            return fn(*args, **kwargs)
+
     try:
-        db.set_last_checked(url)
-        db.add_history(manga_url=url, event_type="check_started")
+        await db_call(db.set_last_checked, url)
+        await db_call(db.add_history, manga_url=url, event_type="check_started")
         await emit({"type": "check_started", "url": url})
 
         # Резолвим источник
         source = get_source_for_url(url, db)
         if source is None:
-            manga_row = db.get_manga(url)
+            manga_row = await db_call(db.get_manga, url)
             if manga_row and manga_row.get("source_id"):
                 source = registry.get_by_db_id(manga_row["source_id"], db)
         if source is None:
@@ -355,7 +361,8 @@ async def check_for_updates(
                 return []
 
             # Обновляем pub_status и количество глав
-            db.update_manga_info(
+            await db_call(
+                db.update_manga_info,
                 url,
                 title=manga.title_ru or manga.title,
                 chapters_total=len(manga.chapters),
@@ -365,12 +372,13 @@ async def check_for_updates(
             )
 
             # Находим главы которых ещё нет в БД
-            known = {ch["chapter_url"] for ch in db.get_all_chapters(url)}
+            known = {ch["chapter_url"] for ch in await db_call(db.get_all_chapters, url)}
             new_chapters = [ch for ch in manga.chapters if ch.url not in known]
 
             for ch in new_chapters:
-                db.upsert_chapter(url, ch.url, ch.title, ch.number, ch.volume)
-                db.add_history(
+                await db_call(db.upsert_chapter, url, ch.url, ch.title, ch.number, ch.volume)
+                await db_call(
+                    db.add_history,
                     manga_url=url,
                     event_type="new_chapter_found",
                     chapter_url=ch.url,
@@ -386,7 +394,8 @@ async def check_for_updates(
                     "chapter_number": ch.number,
                 })
 
-            db.add_history(
+            await db_call(
+                db.add_history,
                 manga_url=url,
                 event_type="check_done",
                 details=f"Найдено новых: {len(new_chapters)}",