Staff Interview: Rate Limiter and Sessionizer Design

Concepts: pyRateLimiterDesign, pySessionizerDesign, pyDistributedRateLimit

The sliding window rate limiter is a staff interview favorite because it starts as a simple algorithm problem and escalates into systems design, concurrency, and distributed systems all within one question. The algorithm itself -- maintain a deque of request timestamps, evict stale ones, check if under the limit -- takes maybe 10 minutes for an experienced engineer. The real interview is everything that comes after. Let me walk you through each escalation and what the right answer is. Part 1: The Core Algorithm Note I'm using time.monotonic() rather than time.time(). Monotonic time is not affected by system clock adjustments (NTP, leap seconds, DST). For a rate limiter where you're comparing time differences, monotonic time is the correct choice. Mentioning this in the interview signals pr