diff --git a/cognee/infrastructure/databases/cache/cache_db_interface.py b/cognee/infrastructure/databases/cache/cache_db_interface.py
index a70b3fc9c..f98103ea4 100644
--- a/cognee/infrastructure/databases/cache/cache_db_interface.py
+++ b/cognee/infrastructure/databases/cache/cache_db_interface.py
@@ -40,3 +40,40 @@ class CacheDBInterface(ABC):
             yield
         finally:
             self.release()
+
+    @abstractmethod
+    async def add_qa(
+            self,
+            user_id: str,
+            session_id: str,
+            question: str,
+            context: str,
+            answer: str,
+            ttl: int | None = 86400,
+    ):
+        """
+        Add a Q/A/context triplet to a cache session.
+        """
+
+        pass
+
+    @abstractmethod
+    async def get_latest_qa(self, user_id: str, session_id: str, last_n: int = 10):
+        """
+        Retrieve the most recent Q/A/context triplets for a session.
+        """
+        pass
+
+    @abstractmethod
+    async def get_all_qas(self, user_id: str, session_id: str):
+        """
+        Retrieve all Q/A/context triplets for the given session.
+        """
+        pass
+
+    @abstractmethod
+    async def close(self):
+        """
+        Gracefully close any async connections.
+        """
+        pass
diff --git a/cognee/infrastructure/databases/cache/get_cache_engine.py b/cognee/infrastructure/databases/cache/get_cache_engine.py
index 1d22b3e30..c1fa3311c 100644
--- a/cognee/infrastructure/databases/cache/get_cache_engine.py
+++ b/cognee/infrastructure/databases/cache/get_cache_engine.py
@@ -1,8 +1,8 @@
 """Factory to get the appropriate cache coordination engine (e.g., Redis)."""
 
 from functools import lru_cache
+from typing import Optional
 from cognee.infrastructure.databases.cache.config import get_cache_config
-
 from cognee.infrastructure.databases.cache.cache_db_interface import CacheDBInterface
 
 config = get_cache_config()
@@ -51,7 +51,7 @@ def create_cache_engine(
         return None
 
 
-def get_cache_engine(lock_key: str) -> CacheDBInterface:
+def get_cache_engine(lock_key: Optional[str] = None) -> CacheDBInterface:
     """
     Returns a cache adapter instance using current context configuration.
     """