Implement queue-based rate limiter with multi-key limits

Implement a rate limiter with method allow(timestamp) that returns true if a request is allowed under a limit of K requests per rolling window W milliseconds, otherwise false. Assume timestamps are nondecreasing integers. Then extend the API to allow(userId, experience, timestamp) that enforces independent limits: at most Ku requests per W per userId and at most Ke requests per W per experience value. The call should succeed only if both limits are satisfied and it must update both counters atomically. Discuss time and space complexity and how you would garbage-collect stale keys.