I Built My Own API Gateway in Rust — Here's What I Learned

Every backend project I've worked on eventually hits the same wall. You start clean — one service, simple routes, everything works. Then slowly the requirements creep in. "We need rate limiting." "Can we add auth middleware?" "What happens when the user service goes down — does it take everything else with it?" You either bolt these things onto every service individually, copy-paste the same middleware across projects, or pay for a managed gateway like Kong or AWS API Gateway and hope it does what you need. I wanted to actually understand how these things work under the hood. So I'm building one — and this is what I've learned so far. What is Ferrox? Ferrox is a self-hosted, programmable API gateway written entirely in Rust. It sits in front of your backend services and handles everything a production system needs in one place: Dynamic routing — point any path prefix to any upstream service Authentication — JWT and API key validation on protected routes Rate limiting — Redis-backed per-IP and per-API-key limiting Circuit breaking — stops hammering a dead upstream service Response caching — Redis-backed TTL cache per route Real-time observability — WebSocket dashboard with live request stats Prometheus metrics — plug straight into Grafana The idea is simple. Instead of this: Client → Service A (has its own auth, rate limiting, logging) Client → Service B (has its own auth, rate limiting, logging) Client → Service C (has its own auth, rate limiting, logging) You get this: Client | v FERROX (auth, rate limiting, circuit breaking, logging — once) | +--------+--------+ | | | Svc A Svc B Svc C (clean) (clean) (clean) Your services stay clean. Ferrox handles the cross-cutting concerns. Why Rust? Honest answer — I already knew Rust from my backend work. But for a gateway specifically, it felt like the obvious choice. A gateway sits on the critical path of every single request. Every millisecond of latency it adds is latency your users feel. You need predictable performance