Code RoomFixed-window limiter allows burst
HardPrep Room Coding #2862

Fixed-window limiter allows burst

On-callAlgorithms & data structuresSenior–Staff~30 min

You enforce a 1,000 req/min per-tenant limit using a fixed-window counter (reset at the top of each minute). A large tenant intermittently overruns and overwhelms a downstream that's provisioned for ~1,000 req/min: monitoring shows brief ~30-second windows where the downstream sees close to 2,000 req from that one tenant and saturates, even though the limiter reports the tenant never exceeded 1,000 per minute. The limiter logs confirm each one-minute window stayed at or under 1,000. How do you triage and fix the limiter so the downstream stops getting buried?

What a strong answer looks like

Stop the bleeding first (mitigate), then form hypotheses from real signals. Separate root cause from symptom, communicate status as you go, and close with what prevents a repeat.

0:00 of about 30 min
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.