Real-time features are everywhere now. Live notifications. Stock tickers. Activity feeds. And whenever someone says "real-time," most developers immediately think WebSocket.
But here's the thing: WebSocket might be overkill for what you're building.
There's another option that's been hiding in plain sight—Server-Sent Events (SSE). It's a native browser standard, runs over plain HTTP, and handles most one-way real-time scenarios better than WebSocket ever could.
So why doesn't anyone use it? Simple: they either don't know it exists, or they assume it's somehow inferior.
Let's fix that.
The Hidden Cost of WebSocket
WebSocket is powerful. It gives you full-duplex, bidirectional communication. But that power comes with baggage:
Resource hungry. WebSocket is stateful. Each connection ties up server resources. Scaling to millions of connections? That's expensive.
Load balancing is painful. Connections are sticky—they bind to specific servers. Horizontal scaling becomes a puzzle instead of a simple config change.
Reconnection? DIY. When connections drop (and they will), you're responsible for handling reconnection logic. Libraries like Socket.io help, but they add weight.
Two-way when you only need one. If your server just needs to push data to clients—notifications, updates, feeds—why maintain a bidirectional channel?
What SSE Actually Is
Server-Sent Events is deceptively simple. It's just an HTTP request with Content-Type: text/event-stream and a response body that never ends.
Think of it like a web page that keeps loading forever. The server holds the connection open and sends data whenever it has something to share.
That's it. No protocol upgrades. No special handshakes. Just HTTP doing what HTTP does.
Why SSE Often Wins
Dead simple to implement. A few lines of code on both ends. The browser's native EventSource API handles everything.
HTTP-native. Load balancers, proxies, firewalls—they all treat SSE like regular web traffic. No special configuration needed.
Auto-reconnect built in. Connection drops? The browser reconnects automatically and sends Last-Event-ID so the server can resume where it left off. You get this for free.
Parallel streams on one connection. HTTP/2 lets you run multiple SSE streams over a single connection. WebSocket typically needs one connection per channel.
Infrastructure friendly. Your existing HTTP tooling just works. Monitoring, logging, caching—all the stuff you've already set up.
When to Use What
Choose SSE when:
- Server pushes data to clients (one-way)
- Notifications, live feeds, stock prices, progress updates
- You want simplicity over complexity
- Your infrastructure is HTTP-based
Choose WebSocket when:
- True bidirectional communication is needed
- Real-time games, collaborative editing, chat with typing indicators
- Sub-millisecond latency matters
- You need binary data streaming
The Bottom Line
Don't reach for WebSocket by default. Ask yourself: does my client actually need to send real-time data back to the server?
If the answer is no, SSE is probably what you want. It's lighter, simpler, and designed exactly for this use case.
Sometimes the boring solution is the right one.