In what situations would AJAX long/short polling be preferred over HTML5 WebSockets?

javascript

ajax

websockets

polling

byNikita Barsukov·Jan 21, 2025

Opt for AJAX polling over WebSockets when grappling with:

WebSocket Incompatibility: If your technical ecosystem or user's browsers lack WebSocket capabilities.
Simplicity Over Complexity: For low-traffic apps where AJAX’s simplicity outweighs WebSocket's sophistication.
Legacy Systems: Where traditional HTTP requests are the only viable method.
Random Data Updates: Ideal when updates are not consistent, thus avoiding holding a WebSocket connection pointlessly.

AJAX short polling example:

setInterval(() => {
  fetch("server_endpoint").then(response => response.json()).then(data => {
    console.log("Data:", data); // Think of JSON data as treasure, and we just found the X on the map!
  });
}, 5000); // If wisdom comes from experience, straight-up downloaded that wisdom every 5 seconds!

This code periodically fetches data from the server every 5 seconds in search of 'treasure'!

Understand the Technology Landscape

Assess the technological landscape and your application's specific requirements:

Use AJAX long polling as a fallback in settings where WebSockets might be overkill or impractical.
Server-Sent Events (SSE) can be a preferable option when you only require server-to-client communication.
Evaluate server load effect. AJAX long polling can put undue strain on resources, whereas WebSockets retain a persistent yet efficient connection.

Simplicity Matters: AJAX for Quick and Easy Solutions

Quick deployment for prototyping

Here's when you might consider AJAX polling over WebSockets:

Resource Limitations: In server situations not designed for managing WebSocket connections, opting for AJAX prevents resource-intensive changes.
Progressive Enhancement: Implement AJAX polling as a starting point and refine the user experience as per requirement, enabling a gradual build-up for superior capabilities.
Development Agility: Fast prototype construction or minimum viable products can leverage AJAX's streamlined integration, prioritizing swift execution over performance.

When architectural simplicity is obligatory

Consider polling methods for the sake of architecture and infrastructure ease:

If your infrastructure is strictly HTTP-reliant, and accommodating WebSockets entails significant overhaul.
When aiming to hit the sweet spot between real-time functionality and budget constraints, AJAX polling could be your ticket.

A Nod to Developer Experience

Keeping development workflow smooth

Let's compare the developer experience:

Lower Learning Curve: AJAX sticks to the standard request-response protocol which most developers are accustomed to.
Troubleshooting made easy: Standard HTTP requests are more straightforward to inspect and debug thanks to browser-based developer tools or networking software.
Fits seamlessly into architecture: Introducing AJAX to a system doesn't necessitate altering how the back-end processes requests, unlike a WebSocket revamp for full-duplex communication.

Keeping security concerns in check

Reflect upon the security implications when deciding:

Security Frameworks: While AJAX comfortably leverages HTTPS security framework, WebSockets (using the ws:// or the secure wss:// protocol) may compel additional security assessments.
Firewall Adherence: AJAX, being a standard HTTP protocol, hardly faces firewall issues, whereas firewalls might block WebSocket connections.

Fostering cost-effective communication

Balancing communication overhead:

AJAX polling might lead to higher overheads due to recurrent HTTP headers; on the other hand, WebSockets, post the initial handshake, exchange mutually understandable data frames.
For use-cases like a live chat system, where continuous updates are essential, WebSockets can provide the required speed and efficiency, leaving AJAX far behind.

Bolstering Application Architecture

Planning for long-term stability

Think about long-term implications for your project:

A stable WebSocket implementation lays the foundation for smooth scaling, mitigating performance issues linked with scaling AJAX polling.
Consider mature WebSocket servers like Socket.IO or WebSockets in Node.js for their innate scaling capabilities.

Success stories and lessons

Glean insights from successful integrations:

Chat Applications: AJAX may seem easier at first for chat apps, however, as users multiply, the persistent connection of WebSockets ensures optimal latency.
Stock Market Apps: Financial apps requiring frequent updates demand low-latency data streaming. Here, WebSockets outshine AJAX polling that inherently suffers from data delay.