A full system design of a production rate limiter. Covers every major algorithm (token bucket, sliding window, leaky bucket, fixed window), their tradeoffs, how they break in a distributed system, how Redis fixes them, and how Stripe, Cloudflare, and API gateways actually deploy this in production.

Your background jobs crash on deployment, fail silently, and corrupt data. Here's how to fix it with worker pools, retry strategies, idempotency, and graceful shutdown. A guide to building production background processing systems that don't break under load. Tested at 20 req/sec.