How do you implement a load balancer in Node.js?

Question

Accepted Answer

**Load balancer** — distributes incoming requests across multiple servers.

```javascript
const http = require("http");
const httpProxy = require("http-proxy");

const proxy = httpProxy.createProxyServer({});

const servers = [
    "http://localhost:3001",
    "http://localhost:3002",
    "http://localhost:3003",
];

let currentIndex = 0;

// Round-robin
function getNextServer() {
    const server = servers[currentIndex];
    currentIndex = (currentIndex + 1) % servers.length;
    return server;
}

lb.listen(80, () => console.log("Load balancer on port 80"));
```

**Strategies:**
- **Round-robin** — cycle through servers.
- **Least connections** — route to least busy.
- **IP hash** — consistent routing.
- **Weighted** — based on server capacity.

**For production, use:** Nginx, HAProxy, or cloud LB.

Node.js: How do you implement a load balancer in Node.js?