Scaling and Securing WebSocket Connections

WebSockets are essential for real-time applications—from trading engines to AI assistants. But when you move from prototype to production, things get tricky. Especially when uptime, load balancing, and secure communication matter.

Here’s how I approach scaling WebSocket backends in high-availability environments without compromising security or developer experience.

Persistent Connections Meet Distributed Systems

WebSockets maintain a long-lived TCP connection, which breaks traditional stateless load balancing. That’s where session affinity (sticky sessions) come in.

NGINX, HAProxy, and most managed load balancers like AWS ALB*support sticky sessions based on cookies or IP hashing. This ensures clients consistently route to the same backend node, keeping their connection alive.

Secure It: wss:// or Bust

You should never run production WebSockets over ws://. Always use wss:// (TLS-encrypted).

You can terminate TLS at the load balancer (e.g., Cloudflare or NGINX) and forward traffic to internal nodes over plain TCP. Just make sure to:

• Use valid certificates (Let’s Encrypt or managed)
• Redirect all insecure connections
• Set proper CORS policies if the frontend is hosted separately

Auth Is Not Optional

WebSocket connections don’t support traditional HTTP headers after the handshake. So you need to authenticate early and smartly.

I usually go with:

• JWT-based auth on connection
• Validated via query string or an initial message payload
• Optionally, revalidate tokens periodically in long sessions

Pair that with Redis or Kafka for coordinating presence, rate-limiting, or propagating bans across nodes.

Redis Pub/Sub: The Backbone of Multi-Node Messaging

In multi-instance setups, your WebSocket servers need to communicate. If one user connects to Node A, and their friend connects to Node B, how do they chat?

Simple: publish to a central broker. I usually default to Redis Pub/Sub for simplicity and speed. If you need durability or streaming, go Kafka.

Bun WebSocket: A New Performance Baseline

If you're building with Bun, you get access to its fast native WebSocket implementation.

Bun WebSocket is extremely lightweight and handles thousands of concurrent connections with low memory overhead. You can:

• Launch a standalone server using Bun's serve() with native upgrade handling
• Integrate with Redis Pub/Sub or a shared memory queue
• Use Bun's edge-focused performance to run it close to users

It’s a solid choice for edge-native, low-latency real-time apps.

Rate-Limiting, Monitoring, and DDoS Protection

Never expose a WebSocket server directly to the open internet without protection. Use:

• Cloudflare or a WAF in front
• Basic IP-based rate limiting at the load balancer
• Application-level limits for messages per second/user
• Logging and metrics via Prometheus, Datadog, or Sentry

TL;DR Checklist

• Sticky sessions via load balancer (cookie or IP hash)
• TLS with wss:// only
• Token-based auth handshake
• Redis for pub/sub or shared state
• Bun WebSocket for low-latency edge-native performance
• Rate limiting + monitoring
• Health checks and auto-scaling

Whether it’s Web3 trading apps, multiplayer UIs, or streaming AI results. WebSockets are powerful, but they demand a clear architecture to scale securely.