API Rate Limiter

Problem Statement:

You are tasked with implementing an API rate limiter. The goal is to restrict users such that they can only perform a maximum of N API calls in any rolling 60-second window. Each user is independent and should have their own rate limiting.

Requirements:

• Implement a class called RateLimiter with at least the following method:
  • request(user_id: string, timestamp: int) -> bool
    • This method will be invoked every time a user makes an API call. The timestamp parameter represents the time of the request in seconds.
    • It should return True if the API call is allowed under the rate limit or False if the user has already reached the maximum allowed calls in the past 60 seconds.
• The rate limiter should work on a rolling window basis, meaning that it always considers the past 60 seconds from the current request time.
• The value of N (maximum allowed calls per 60-second window) should be configurable.
• The solution should handle multiple users concurrently, ensuring that each user’s calls are tracked separately.

Example:

Assume N is set to 3 for a particular user:

• For user "Alice", if API calls are made at times 1, 20, and 50 seconds, all three should be allowed.
• A fourth call at time 55 seconds should be rejected (return False) because it is within the 60-second window containing 3 calls.
• If a call is made at time 62 seconds and one or more of the earlier calls have fallen out of the 60-second window, the call should be allowed.

Additional Constraints:

• Optimize your solution for efficiency, as the method may be called frequently under high load.
• Do not use external libraries for handling the time window; implement the necessary logic yourself.

Your task is to implement the class RateLimiter according to the above specifications.