Explain WebSocket vs SSE vs Long Polling.

Example

Think of a live cricket score app: WebSockets update scores instantly both ways, SSE streams updates one-way, and long polling keeps asking the server for new scores repeatedly.

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Why Is It Important

Choosing the right approach directly impacts latency, scalability, and user experience in real-time systems.

Interview Tips

In interviews, clearly define each:

• WebSockets = two-way persistent connection.
• SSE = one-way server push.
• Long polling = repeated HTTP requests. Then, tie them to practical examples (chat app, notification feed, etc.).

Trade-offs

• WebSockets: low-latency but needs persistent connections.
• SSE: simple, lightweight, but one-way only.
• Long polling: works anywhere but high server overhead.

Pitfalls

• Using SSE where client-to-server updates are required.
• Relying on long polling for high-frequency events (server overload).
• Forgetting reconnection handling in WebSockets or SSE.