simple rate-limiter interview question

ratelimter.js

/*
  We want to build a rate limiter system for a frontend which receives requests
  at whole seconds. Assume we have all the requests over an interval of time
  represented as an array, e.g., requests = [0,0,1,1,1,2,2] The index is the
  reauest ID and the value is the time stamp.

  Design a rate limiter that can enforce a limit of Q requests per T seconds.
  The output should return the timestamp of dropped requests as well as the
  request IDS.


  eg 1
  Requests  = [0, 0, 1, 1, 1, 2, 2];
  For Q = 2 and T = 1 we get
  Dropped times = [1]
  Dropped requests = [4]

  eg 2
  Requests = [0, 0, 0, 1, 1, 2, 2, 2]
  For Q = 2, T = 2, we get
  Dropped times = [0, 1, 2]
  Dropped requests = [2, 3, 4, 7]

 */

const example1 = [0, 0, 1, 1, 1, 2, 2];
const example2 = [0, 0, 0, 1, 1, 2, 2, 2];

function getBucket(r, t) {
  return Math.floor(r / t);
}

function processRequests(q, t, requests) {
  const droppedRequests = [];
  const droppedTimes = new Set();
  const buckets = {};

  for (let i = 0; i < requests.length; i++) {
    let b = getBucket(requests[i], t);
    if (buckets[b]) {
      buckets[b]++;
      if (buckets[b] > q) {
        // check if bucket has exceeded limit
        droppedTimes.add(requests[i]);
        droppedRequests.push(i);
      }
    } else {
      buckets[b] = 1;
    }
  }

  return {
    buckets,
    droppedTimes: Array.from(droppedTimes),
    droppedRequests,
    requests,
    q,
    t,
  };
}

const eg1 = processRequests(2, 1, example1);
const eg2 = processRequests(2, 2, example2);

console.log(eg1);
console.log(eg2);

Output

{
  buckets: { '0': 2, '1': 3, '2': 2 },
  droppedTimes: [ 1 ],
  droppedRequests: [ 4 ],
  requests: [
    0, 0, 1, 1,
    1, 2, 2
  ],
  q: 2,
  t: 1
}
{
  buckets: { '0': 5, '1': 3 },
  droppedTimes: [ 0, 1, 2 ],
  droppedRequests: [ 2, 3, 4, 7 ],
  requests: [
    0, 0, 0, 1,
    1, 2, 2, 2
  ],
  q: 2,
  t: 2
}