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.

A complete system design of Relay, a multi-tenant AI API gateway. Covers multi-tenant database architecture (silo vs pool vs bridge), API key authentication, provider routing with failover, dual-layer rate limiting, token-based billing, response caching, row-level security, tenant provisioning, and observability. Full Postgres schemas, mermaid diagrams, and Go snippets included.

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.