When should you use SSE vs Polling vs WebSockets?

When building real-time applications, developers usually consider three approaches: Polling Server-Sent Events (SSE) WebSockets At first, they may seem similar. But choosing the wrong one can lead to performance issues, complexity, or scalability problems . Let’s break them down clearly. 🔁 1. Polling — The Simplest Approach Polling means the client repeatedly asks the server for updates. Example: Client → “Any update?” Server → “No” Client → “Any update?” Server → “No” Client → “Any update?” Server → “Yes” ✅ Pros Very easy to implement Works everywhere ❌ Cons Wastes bandwidth (many useless requests) High server load Delayed updates ⚡ 2. Server-Sent Events (SSE) With SSE, the client opens a single connection and waits for updates. Client → open connection Server → send updates when ready Server → send updates when ready SSE uses standard HTTP and the browser API: EventSource ✅ Pros Efficient (no repeated requests) Simple to implement Built-in reconnection Works over HTTP ❌ Cons One-way