41. Token Bucket Rate Limiter

function consume(b, now) {
  const elapsed = (now - b.last) / 1000;
  b.tokens = Math.min(b.capacity, b.tokens + elapsed * b.rate);
  b.last = now;
  if (b.tokens >= 1) {
    b.tokens -= 1;
    return true;
  }
  return false;
}