BackendFrontend
WebSockets
Also written as Socket.io
A protocol that keeps a persistent, two-way connection open between a client and server, so either side can send data anytime — used for real-time features like chat or live updates.
Think of it like
Like an open phone line both sides can talk into anytime, instead of REST's back-and-forth of hanging up and re-calling for every single question.
Junior or senior?
Junior sounds like
Has implemented the happy-path WebSocket connection.
Senior sounds like
Has handled what happens when that connection drops mid-session.
Ask them
“How did your app handle a WebSocket connection dropping mid-session?”