3 posts tagged with "backend"

When software engineers talk about WebSockets, the conversation usually focuses on client-side APIs (new WebSocket(url)), backend message handlers, or high-level Pub/Sub abstractions. We treat connections as lightweight objects in our code that magically stay alive and receive real-time updates.

But what actually happens underneath your application runtime? What is the Operating System kernel doing when your server maintains 100,000 or 1,000,000 concurrent WebSocket connections?

In this article, we are stepping away from high-level application frameworks to explore WebSockets at the OS level. We will inspect how Linux manages persistent TCP sockets, how event demultiplexing like epoll enables high concurrency, how kernel socket buffers consume system RAM, and how sysctl kernel tuning prevents your real-time infrastructure from falling over under load.

Understanding these OS-level mechanics changes how you architect, debug, and scale real-time applications.

The perspective I rarely see (and why I’m writing this)​

Most “what are WebSockets” articles explain the API and stop there. That helps you demo a chat, but it does not help you ship real time features that survive load spikes, deploys, mobile networks, and annoying edge cases.

I’m writing this because, in 2026, WebSockets are not a novelty, they are a reliability problem you either solve once (well), or keep re learning in production. If you want real time UX without building a whole messaging infrastructure, you need the mental model, plus a checklist you can actually follow, and a platform that removes the sharp edges.

WebSockets are often described as “a persistent connection between client and server”, but that definition hides most of the complexity and the real power behind the protocol.

In this How WebSockets Work deep dive, I want to go beyond surface level explanations and break down what actually happens at the protocol, infrastructure, and architectural level. This perspective comes from building Ressonance, an open source WebSocket as a Service platform, and seeing firsthand where teams struggle when moving from request based systems to real time communication.

If you are building dashboards, notifications, collaborative tools, or any system that depends on real time communication, understanding how WebSockets really work is not optional.