Introduction

Real-time functionality is no longer a luxury. Whether you're building a chat app, a stock ticker, or a multiplayer game, users expect updates as they happen.

But there’s more than one way to deliver real-time features on the web.

When I started building a multi-tenant real-time ChatAPI, I ran into this question early:

Should I use REST with polling? Server-Sent Events? WebSockets?

Turns out — each method has trade-offs.

In this post, I’ll break down four popular options:

• Polling
• Long Polling
• Server-Sent Events (SSE)
• WebSockets

And I’ll tell you exactly when each one makes sense, with real examples.

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1. 🌀 Polling

How it works:
The client sends a request at a fixed interval to ask:

“Do you have anything new?”

setInterval(() => {
  fetch('/api/messages').then(renderMessages);
}, 3000);

Pros:

• Simple to implement

• Works with any backend

Cons:

• Delayed response (worst-case latency = polling interval)

• Wastes resources with empty requests

• Poor scalability

• When to use:

• Data updates slowly (e.g. checking a report every 30s)

• You want a dead-simple approach for MVPs

2. 🔁 Long Polling

How it works:
The client sends a request and the server holds it open until new data is available.

When data arrives, the server responds — then the client sends another request.

function longPoll() {
  fetch('/api/messages/stream')
    .then(res => res.json())
    .then(data => {
      render(data);
      longPoll(); // repeat
    });
}

Pros:

• More responsive than polling

• Compatible with older HTTP infrastructure

Cons:

• Still HTTP-based: repeated connections, overhead

• Slight delay between disconnect + reconnect

When to use:

• You’re stuck with HTTP/1.1 and can't use WebSockets

• You need better latency than basic polling

3. 📡 Server-Sent Events (SSE)

How it works:
SSE lets the server push updates to the client over a single HTTP connection using the EventSource API.

const source = new EventSource('/events');
source.onmessage = (event) => {
  render(JSON.parse(event.data));
};

Pros:

• Built into the browser

• Lightweight and efficient

• Automatic reconnection

Cons:

• One-way only (server → client)

• Only works over HTTP, not HTTPS/2 with full bi-directional support

• Limited support outside browsers (e.g., mobile/websocket clients)

When to use:

• You only need server-to-client updates

• You're building dashboards, notifications, or analytics

• You want something simpler than WebSockets

4. 🌐 WebSockets

How it works:
A full-duplex connection where both client and server can send messages in real time — using a single TCP connection.

const socket = new WebSocket('wss://chat.example.com/ws');
socket.onmessage = (event) => {
  render(JSON.parse(event.data));
};

Pros:

• True bi-directional communication

• Low latency, persistent connection

• Ideal for real-time apps (chat, games, collab tools)

Cons:

• Slightly more complex setup

• Not always supported by older firewalls/proxies

• Not ideal for low-frequency, one-way updates

When to use:

• Real-time chat, multiplayer games, live editing

• You need instant, two-way communication

• You want scalable real-time experience with low overhead

As i concluded, choosing a real-time strategy isn't just about what's trending — it's about what fits.