Top 49 WebSockets & Real-time Interview Questions & Answers (2026)

01 What is WebSocket? 02 How does WebSocket differ from HTTP? 03 What is the WebSocket handshake? 04 What is real-time communication? 05 What are common use cases for WebSockets? 06 What is Socket.IO? 07 What is the difference between WebSockets and Server-Sent Events (SSE)? 08 What is long polling? 09 What is the WebSocket protocol (ws:// and wss://)? 10 How do you create a WebSocket connection in JavaScript? 11 What events does a WebSocket connection have? 12 What is a WebSocket frame? 13 How do you send data over a WebSocket connection? 14 What is a WebSocket ping/pong? 15 What happens when a WebSocket connection is lost? 16 What is Socket.IO's fallback mechanism? 17 How does a chat application use WebSockets? 18 How do you close a WebSocket connection? 19 What browsers support WebSockets? 20 What triggers can break a WebSocket connection?

01 How do you implement a WebSocket server in Node.js using the `ws` library? 02 What are Socket.IO rooms and namespaces? 03 How do you handle WebSocket reconnection logic? 04 What is the difference between Socket.IO and raw WebSockets? 05 How do you authenticate WebSocket connections? 06 How do WebSockets work behind a load balancer? 07 What is Redis Pub/Sub and how does it help with WebSocket scaling? 08 How do you implement presence (online/offline) with WebSockets? 09 What is the WebSocket subprotocol? 10 How do you handle binary data over WebSockets? 11 How do you broadcast messages to multiple clients? 12 What are the security considerations for WebSocket connections? 13 How does message ordering work in WebSockets? 14 What is backpressure in WebSocket communication? 15 How do you test WebSocket applications? 16 How do WebSockets interact with firewalls and proxies? 17 What is STOMP protocol and how is it used with WebSockets? 18 What is the maximum message size for WebSockets? 19 How do you monitor and debug WebSocket connections?

01 How do you scale WebSocket servers horizontally? 02 What is the difference between WebSockets and WebRTC? 03 How do you implement end-to-end encryption over WebSockets? 04 What is the actor model and how does it apply to real-time systems? 05 How do you handle WebSocket connections in a Kubernetes environment? 06 What is CRDT (Conflict-free Replicated Data Type) and how does it apply to real-time collaboration? 07 How do you implement rate limiting for WebSocket connections? 08 What are the memory implications of maintaining many WebSocket connections? 09 How do you implement a distributed WebSocket system with message ordering guarantees? 10 What is the Phoenix Framework's approach to real-time communication with channels?