diff --git a/backend/backend/db/base_class.py b/backend/backend/db/base_class.py
index 71b9703..69b1d62 100644
--- a/backend/backend/db/base_class.py
+++ b/backend/backend/db/base_class.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from logging import getLogger
-from typing import Iterable, Self, TYPE_CHECKING
+from typing import Self, Sequence, TYPE_CHECKING
 
 from sqlalchemy import select
 from sqlalchemy.exc import IntegrityError
@@ -17,21 +17,34 @@ class Base(DeclarativeBase):
     db: Database | None = None
 
     @classmethod
-    async def add(cls, objs: Self | Iterable[Self]) -> bool:
+    async def add(cls, objs: Sequence[Self]) -> bool:
+        if cls.db is not None and (session := await cls.db.get_session()) is not None:
+
+            try:
+                async with session.begin():
+                    session.add_all(objs)
+
+            except IntegrityError as err:
+                logger.warning(err)
+                return await cls.merge(objs)
+
+            except AttributeError as err:
+                logger.error(err)
+                return False
+
+        return True
+
+    @classmethod
+    async def merge(cls, objs: Sequence[Self]) -> bool:
         if cls.db is not None and (session := await cls.db.get_session()) is not None:
 
             async with session.begin():
-                try:
-                    if isinstance(objs, Iterable):
-                        session.add_all(objs)
-                    else:
-                        session.add(objs)
+                for obj in objs:
+                    await session.merge(obj)
 
-                except (AttributeError, IntegrityError) as err:
-                    logger.error(err)
-                    return False
+            return True
 
-        return True
+        return False
 
     @classmethod
     async def get_by_id(cls, id_: int | str) -> Self | None: