Distributed Rate Limiter System Design
System design for a distributed rate limiter. Uses Redis sorted sets with sliding window log algorithm to track request counts per client. Configurable rules stored in a Rules DB define per-endpoint limits. Returns 429 when limits are exceeded.
rate limitersystem designredisdistributed systemsapi gateway
Requirements
Functional
- Limit requests per client per time window
- Return 429 status when limit exceeded
- Support configurable rate limit rules
- Track request counts in real-time
Non-Functional
- Sub-millisecond latency for rate checks
- Horizontally scalable across data centers
- Highly available (fail-open on Redis failure)
- Accurate counting under high concurrency
Author
Published
February 17, 2026
Last updated February 17, 2026