I built a Load Balancer from Scratch - Every Request Is a Lie

Why a Load Balancer Looks Simple (Until It Breaks) This is a Layer 7 (application layer) load balancer. It operates at the HTTP level — it understands requests, URLs, headers, and status codes. A Layer 4 load balancer works at the TCP level: it forwards raw bytes without knowing what protocol is inside. L7 is slower (it has to parse HTTP) but smarter (it can route based on path, retry on 5xx, health check via GET /health ). Everything in this project — routing decisions, health checks, retry logic — depends on understanding HTTP. A load balancer does one thing: receive a request, pick a backend, forward it. In the happy path, it's ~20 lines of code. The complexity comes when things fail — and things always fail. This is not a tutorial. It's what I learned building one from scratch with Node.js and zero dependencies. Step 1: The Reverse Proxy A reverse proxy sits between the client and the backend. The client talks to the proxy, the proxy talks to the backend. The client never knows the