Compare WebSockets, Server-Sent Events and long polling. Which would you use for a chat app, a live dashboard and occasional job-status updates?

Use WebSockets for chat, SSE for a live dashboard, and polling or SSE for occasional job status.

Long polling: the client sends a request. The server holds it open until there is news or a timeout. Then the client asks again right away. It works everywhere over plain HTTP. But it costs one request per message, and it adds delay.

SSE (Server-Sent Events): the client opens one HTTP request. The server streams text/event-stream messages down it.

• It goes one way only, from server to client.
• It carries text only.
• EventSource gives built-in reconnection and Last-Event-ID, so the client can continue from the last message it got.
• It works with normal HTTP infrastructure.

WebSockets: an HTTP upgrade turns the connection into a full-duplex channel. Both sides can send text or binary frames at any time, with little overhead.

Why each choice:

• Chat needs both directions with low delay, so use WebSockets.
• A live dashboard only receives data, so SSE is simpler.
• Occasional job status can use plain polling, long polling, or SSE.