diff --git a/src/dsa/caching_memoization.py b/src/dsa/caching_memoization.py
index 20390ec..17a31d0 100644
--- a/src/dsa/caching_memoization.py
+++ b/src/dsa/caching_memoization.py
@@ -6,24 +6,25 @@ def time_based_cache(expiry_seconds: int) -> Callable:
     """Manual implementation of a time-based cache decorator."""
 
     def decorator(func: Callable) -> Callable:
-        cache: dict[str, tuple[Any, float]] = {}
+        cache: dict[tuple, tuple[Any, float]] = {}
 
         def wrapper(*args, **kwargs) -> Any:
-            key_parts = [repr(arg) for arg in args]
-            key_parts.extend(f"{k}:{repr(v)}" for k, v in sorted(kwargs.items()))
-            key = ":".join(key_parts)
+            # Use hashable tuples for the cache key for speed
+            if kwargs:
+                key = (args, frozenset(kwargs.items()))
+            else:
+                key = (args, None)
 
             current_time = time.time()
 
-            if key in cache:
-                result, timestamp = cache[key]
+            cached = cache.get(key)
+            if cached is not None:
+                result, timestamp = cached
                 if current_time - timestamp < expiry_seconds:
                     return result
 
             result = func(*args, **kwargs)
-
             cache[key] = (result, current_time)
-
             return result
 
         return wrapper
@@ -89,4 +90,4 @@ def knapsack(weights: list[int], values: list[int], capacity: int, n: int) -> in
     return max(
         values[n - 1] + knapsack(weights, values, capacity - weights[n - 1], n - 1),
         knapsack(weights, values, capacity, n - 1),
-    )
\ No newline at end of file
+    )