HTTP is a polite conversation. You speak, I listen. WebSockets are a walkie-talkie channel that is permanently left open.
1The HTTP Limitation
HTTP is 'stateless' and 'half-duplex'. The server is deaf and mute until the client makes a request. If you want to know if a friend sent you a message, your app has to use 'Polling'. Polling means running a setInterval loop that executes fetch('/messages') every 2 seconds. If millions of users are online, that's millions of pointless network requests hitting your server every second, mostly returning 'No new messages'. It is a massive waste of CPU and bandwidth.
async function execute() {
// See concept above
}
2The Full-Duplex Solution
WebSockets (ws:// or wss://) establish a persistent, 'full-duplex' connection. The client connects once. The connection stays alive in the background. Now, the server can spontaneously 'push' data down to the client at the exact millisecond an event happens. When your friend hits 'Send' on a message, the server instantly routes it down the open socket to your phone. No polling required.
async function execute() {
// See concept above
}
3When to use WebSockets
WebSockets are stateful. Holding open 50,000 connections requires a massive amount of RAM on your Node.js server. If your server restarts, all 50,000 connections drop instantly. Therefore, you do NOT use WebSockets for standard CRUD operations (like loading an article). You use a Hybrid Architecture: HTTP/REST handles the bulk of the heavy lifting, and WebSockets are strictly reserved for the tiny slivers of data that demand sub-second latency (like live cursors, chats, and notifications).
async function execute() {
// See concept above
}
