WebSocket vs Polling vs SSE — Choosing the Right Real-Time Strategy

Not everything needs WebSockets#

"We need real-time updates" doesn't automatically mean WebSockets. There are three main approaches, and the right one depends on your use case.

Short polling#

The simplest approach: the client asks the server for updates on a regular interval.

Client: Any new messages? (every 5 seconds)
Server: Nope.
Client: Any new messages?
Server: Nope.
Client: Any new messages?
Server: Yes, here's one.

Pros: Dead simple. Works everywhere. No special infrastructure. Cons: Wasteful — most requests return nothing. Latency equals your polling interval.

Use when: Dashboard that updates every 30 seconds. Background sync for non-urgent data. Simple health checks.

Long polling#

The client sends a request, and the server holds it open until there's new data (or a timeout).

Client: Any new messages? (hangs open)
... 30 seconds pass ...
Server: Yes, here's one.
Client: Any new messages? (immediately re-connects)

Pros: Near real-time without WebSocket complexity. Works through all firewalls and proxies. Cons: Still one connection per request cycle. Higher server resource usage from held connections. Ordering can be tricky.

Use when: Chat applications that need simplicity. Notifications where sub-second latency isn't critical. When WebSocket infrastructure isn't available.

Server-Sent Events (SSE)#

The server pushes events to the client over a single long-lived HTTP connection. One-directional: server → client only.

Client: Opens connection to /events
Server: data: {"type":"message","text":"Hello"}\n\n
Server: data: {"type":"message","text":"World"}\n\n
... connection stays open ...

Pros: Built into browsers (EventSource API). Auto-reconnect with last-event-ID. Works over standard HTTP. Simple server implementation. Cons: One-directional only. Limited to ~6 connections per domain in some browsers. No binary data.

Use when: Live feeds, stock tickers, notifications, build logs, AI streaming responses. Anywhere the server pushes and the client listens.

WebSocket#

Full-duplex, bidirectional communication over a single TCP connection. Both client and server can send messages at any time.

Client ↔ Server: persistent connection
Client: sends message
Server: sends message
(both directions, any time)

Pros: True bidirectional. Low latency. Low overhead per message (no HTTP headers). Binary data support. Cons: More complex infrastructure (sticky sessions, connection management). Doesn't work through some corporate proxies. Need heartbeat/ping to detect dead connections.

Use when: Chat applications, multiplayer games, collaborative editing, live trading platforms. Anywhere both sides need to send data frequently.

The decision framework#

Scaling considerations#

Short polling: Scales easily — it's just regular HTTP requests. Use CDN caching for public data.

SSE: Each connected client holds an open HTTP connection. 10,000 users = 10,000 connections. Most web servers handle this fine with async I/O (Node.js, Go, Rust).

WebSocket: Same connection scaling as SSE, plus you need sticky sessions (the same client must hit the same server). Use Redis Pub/Sub to broadcast messages across multiple WebSocket servers.

Long polling: Hardest to scale. Each pending request consumes a server thread/connection. Similar to SSE but with more overhead from repeated connection setup.

The hybrid approach#

Most production apps use a mix:

• WebSocket for the core real-time feature (chat, collaboration)
• SSE for notifications and live updates
• Short polling for non-urgent background syncs

Codelit itself uses SSE for AI streaming (server pushes tokens as they're generated) — it's the perfect fit because the client just listens while the AI generates.

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See real-time patterns in action: generate a chat or collaboration system on Codelit.io and explore the WebSocket connections in the architecture.