diff --git a/src/baby_monitor/repositories/token/memory_token.py b/src/baby_monitor/repositories/token/memory_token.py
index 968247f..409c076 100644
--- a/src/baby_monitor/repositories/token/memory_token.py
+++ b/src/baby_monitor/repositories/token/memory_token.py
@@ -16,6 +16,7 @@ class InMemoryTokenRepository(TokenRepositoryInterface):
     def __init__(self) -> None:
         # token -> (user_id, expiry_time)
         self._tokens: dict[str, tuple[int, datetime]] = {}
+        self._default_ttl = 3600  # Store default TTL for sliding expiration
 
     def store(self, token: str, user_id: int, ttl: int = 3600) -> None:
         """Store a token with TTL (time to live in seconds)."""
@@ -23,7 +24,10 @@ class InMemoryTokenRepository(TokenRepositoryInterface):
         self._tokens[token] = (user_id, expiry)
 
     def verify(self, token: str) -> int | None:
-        """Verify token and return user_id if valid, None otherwise."""
+        """Verify token and return user_id if valid, None otherwise.
+        
+        Implements sliding expiration: extends token lifetime on each verification.
+        """
         if token not in self._tokens:
             return None
 
@@ -34,6 +38,10 @@ class InMemoryTokenRepository(TokenRepositoryInterface):
             del self._tokens[token]
             return None
 
+        # Sliding expiration: extend the token lifetime
+        new_expiry = datetime.now(UTC) + timedelta(seconds=self._default_ttl)
+        self._tokens[token] = (user_id, new_expiry)
+
         return user_id
 
     def invalidate(self, token: str) -> None:
diff --git a/src/baby_monitor/repositories/token/redis_token.py b/src/baby_monitor/repositories/token/redis_token.py
index 6e9a364..52abda5 100644
--- a/src/baby_monitor/repositories/token/redis_token.py
+++ b/src/baby_monitor/repositories/token/redis_token.py
@@ -21,6 +21,7 @@ class RedisTokenRepository(TokenRepositoryInterface):
             redis_client: Redis client instance from redis.from_url()
         """
         self.redis = redis_client
+        self.default_ttl = 3600  # Store default TTL for sliding expiration
 
     def store(self, token: str, user_id: int, ttl: int = 3600) -> None:
         """Store a token with TTL (time to live in seconds)."""
@@ -28,10 +29,15 @@ class RedisTokenRepository(TokenRepositoryInterface):
         self.redis.setex(key, ttl, str(user_id))
 
     def verify(self, token: str) -> int | None:
-        """Verify token and return user_id if valid, None otherwise."""
+        """Verify token and return user_id if valid, None otherwise.
+        
+        Implements sliding expiration: extends token lifetime on verification.
+        """
         key = f"token:{token}"
         user_id_str = self.redis.get(key)
         if user_id_str:
+            # Sliding expiration: extend the token lifetime
+            self.redis.expire(key, self.default_ttl)
             return int(user_id_str)
         return None