WebSockets have become the default answer for 'we need real-time updates,' and they're genuinely the right tool when the client needs to send frequent messages back to the server — a chat application, a collaborative editor, a multiplayer game. A large share of real-time features don't actually need that: they need the server to push updates to the client, one direction only, which is a simpler problem with a simpler solution already built into every browser.
Server-Sent Events do exactly that one-directional job over a plain HTTP connection, with automatic reconnection handled by the browser and no separate protocol to implement on the server. A live notification feed, a dashboard that updates as new data arrives, a progress indicator for a long-running job — none of these need the client talking back over the same channel, and SSE handles them with a fraction of the infrastructure a WebSocket implementation requires.
The infrastructure difference matters more than it first appears. WebSockets need a persistent, stateful connection that load balancers and proxies must be configured to support properly, and scaling them horizontally requires sticky sessions or a message broker to coordinate between server instances. SSE runs over ordinary HTTP, which every piece of existing infrastructure already handles correctly, with no special configuration required.
The decision test is simple: does the client genuinely need to send frequent messages back over the same open connection? If yes, WebSockets are the right tool and the complexity is earned. If the client only occasionally needs to send something — a button click, a form submission — that can go over an ordinary API request alongside an SSE connection for the server-to-client half, which is simpler to build, simpler to scale, and simpler to debug than a WebSocket implementation reaching for capability the feature never uses.
