Cache with Time Limit / TTL

Implement a key-value cache where each entry expires after a specified time-to-live (TTL).

`python class AutoExpireCache: def set(key: str, value: any, ttl_ms: int) -> bool: # Set key with value that expires after ttl_ms milliseconds # Return True if key didn't exist, False if updating existing key

def get(key: str) -> any:
    # Return value if key exists and not expired, otherwise None

def count() -> int:
    # Return count of non-expired keys

`

Follow-ups: Lazy delete vs background cleanup, LRU eviction when memory full.