Interview Simulator · System Design
Design a Rate Limiter
A full 45 minute round, one phase at a time. Each phase has a time budget, follow-up questions from the interviewer, and a checklist for your level. Reveal a phase's model answer whenever you need it; the report shows which phases you earned.
Design a rate limiter for a fleet of 100 services, each taking about 5,000 requests a second. Every API key gets up to N requests a minute per route, the limits hold across the whole fleet, and the check can add no more than 2 ms to p99 latency.