Why Pusher is the Safe Option Over Socket.io in a Serverless Environment

When I was building my chat app, I had to make a decision between Pusher.js and Socket.io. Both can be used to add real-time communication to an application, so I asked myself: what’s the real difference between them? 🤷‍♂️

Pusher.js is a managed cloud service that handles real-time communication for you. Instead of having your own server spin up and manage WebSocket connections, Pusher takes care of that. They provide both client and server SDKs, which you use to connect your app to their infrastructure without worrying about the low-level socket setup.

Socket.io, on the other hand, is a Node.js library built by Guillermo Rauch (the same guy behind Vercel). It helps you set up a WebSocket server more easily, instead of dealing directly with the low-level WebSocket API in Node.js.

So far, Socket.io sounds great — it’s free, open-source, and gives you full control.
But here’s where things get tricky.

The Problem with Serverless

Serverless functions are stateless and short-lived. They spin up, handle a request, wait for external operations (like a database call), and then shut down.
The issue is that WebSocket connections need to stay open for as long as users are connected. When your serverless function shuts down, that connection dies too.

That’s where Pusher comes in. It manages and maintains WebSocket connections for you. Your server doesn’t need to stay alive — it simply triggers events via HTTP calls using the SDKs Pusher provides. Pusher handles the long-lived connections on its own cloud infrastructure, which fits perfectly with the stateless nature of serverless environments.

But All This Comes at a Cost

Pusher isn’t free at scale.

Still, it’s a solid choice for indie projects, prototypes, or SaaS apps hosted on Vercel or similar platforms where reliability and simplicity are worth more than the extra configuration that comes with Socket.io.

Conclusion

If you’re building on a serverless platform, Socket.io will fight your architecture. Pusher embraces it.

Anyway, don’t take this as gospel. I’m just a frontend engineer exploring what works and what doesn’t. You’re the pilot — choose the right tool for your project’s flight path.