QuickReply.ai Full Stack Developer interview questions

You are building an API Rate Limiter for a backend service. Each user is allowed to make at most K requests within a rolling window of T seconds. boolean allowRequest(userId, timestamp) Rules userId is a string. timestamp is an integer representing seconds. Return true if the request is allowed. Return false if the user has already made K requests in the last T seconds. Example K = 3, T = 10 allowRequest("user1", 1) → true allowRequest("user1", 2) → true allowRequest("user1", 3) → true allowRequest("user1", 4) → false allowRequest("user1", 11) → true Constraints Up to 1 million users Requests arrive in non-decreasing timestamp order Solution must be efficient in both time and memory