In one of the recent projects I worked on with my team, we implemented Server-Sent Events (SSE). While it’s a fairly simple concept, I found it difficult to fully grasp how it worked by just reading the articles out there. So, I want to share my learnings in a way that’s easy to follow — something my younger self, who didn’t know a thing about SSE, would have appreciated. If you’re here to understand SSE in the simplest terms, you’re in the right place!
Before diving into the definition of Server-Sent Events (SSE), let’s explore a scenario where you might need it.
Imagine you’re using an e-commerce application. You browse for products, add them to your cart, place an order, and proceed to payment. During payment, you’re redirected to a third-party payment provider. Once the payment is completed and the amount is deducted from your account, you’re redirected back to the e-commerce platform. But how does the e-commerce app know when the payment is successfully processed? And how does the UI automatically transition from a loading screen to a confirmation page showing that the order has been placed?
In this situation, the backend server needs a way to inform the front-end that the payment is completed. Instead of constantly checking the server for updates (which can be inefficient), the front-end can open a persistent connection with the backend, waiting for a notification that the payment has been processed. Once the backend sends a status like “Payment Completed,” the UI can immediately update, showing the confirmation page. This is a perfect example of using SSE.
What is SSE?
Server-Sent Events (SSE) allow a client (usually a web browser) to establish a long-lived, persistent connection to the server. The server can then “push” updates to the client whenever new information is available, and the client listens for these updates to react accordingly. Unlike WebSockets, which offer two-way communication, SSE is a one-way stream where only the server sends updates to the client.
A common use case for SSE is live updates, like stock market prices or live sports scores, where the client needs real-time data .
SSE is simpler than WebSockets when you only need updates from the server to the client.
I hope this gave you a quick idea of what Server-Sent Events are and how they can be used in a real-world scenario. In the next article, I’m planning to share a detailed example of how you can integrate Server-Sent Events into your Kotlin Spring WebFlux application. Thanks for reading till here, and never stop asking questions!!
