Introduction
What Ratelane is and how it works.
Ratelane is an API observability and policy control plane for FastAPI and Node.js (Express, Fastify, Hono).
You add a single middleware to your server. The middleware:
- Discovers your routes automatically on startup
- Sends telemetry (request counts, latency, IP, device info) to Ratelane on a background poll
- Enforces rate limit policies returned from the control plane — without a round-trip on every request
The result is a live dashboard showing traffic across your entire fleet, with per-route policy control you can change without redeploying.
Key concepts
- Fleet — all running instances of your API, grouped by service name
- Policy — per-route rate limit rules (requests/window, burst, block behaviour)
- Emergency Profile — a one-click override that tightens limits across the whole fleet instantly
- Circuit Breaker — automatic protection when an instance exceeds a threshold