WebSocket Interview Guide: Scaling, Security, and Advanced Topics for Experts

Core WebSocket Concepts

1. What are WebSockets, and how do they differ from HTTP?
2. Explain the WebSocket handshake process.
3. How do WebSockets achieve full-duplex communication?
4. What are the key headers involved in a WebSocket upgrade request?
5. What is the role of the Sec-WebSocket-Key header?
6. How does a WebSocket connection transition from HTTP to a persistent connection?
7. Compare WebSockets with Server-Sent Events (SSE).
8. What are subprotocols in WebSockets, and how are they used?
9. How do WebSockets handle binary data?
10. What is the WebSocket protocol’s default port?

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WebSocket Implementation

1. How do you implement WebSockets in Node.js?
2. What is the purpose of the ws library in Node.js?
3. How do you manage WebSocket connections in a Python application?
4. Explain the role of ping/pong frames in WebSockets.
5. How do you close a WebSocket connection gracefully?
6. What are the key methods of the WebSocket API in JavaScript?
7. How do you send and receive messages using WebSockets on the client side?
8. How do you implement authentication in a WebSocket connection?
9. What is the significance of the onopen, onmessage, and onclose events in WebSocket APIs?
10. How do you handle errors in WebSocket connections?

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WebSocket Security

1. How do you secure a WebSocket connection using TLS/SSL?
2. Explain the impact of CORS on WebSockets.
3. How do you prevent Cross-Site WebSocket Hijacking?
4. What is the role of origin headers in WebSocket security?
5. How do you authenticate WebSocket connections using JWT?
6. What are the common vulnerabilities of WebSockets?
7. How do you mitigate denial-of-service (DoS) attacks in WebSockets?
8. Explain the role of rate limiting in securing WebSocket connections.
9. How do you handle sensitive data transmission over WebSockets?
10. What tools can you use for WebSocket security testing?

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Scaling WebSocket Applications

1. What challenges are involved in scaling WebSocket connections?
2. How do you handle a large number of concurrent WebSocket connections?
3. What is horizontal scaling, and how does it apply to WebSocket servers?
4. How do load balancers like Nginx or HAProxy handle WebSocket traffic?
5. What is the role of sticky sessions in WebSocket scaling?
6. How do you manage WebSocket connections in a distributed architecture?
7. Explain the use of message brokers like Redis or Kafka in WebSocket scaling.
8. How do WebSocket servers use pub/sub patterns?
9. What is backpressure, and how do you handle it in WebSocket servers?
10. How does a WebSocket server handle connection timeouts?

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WebSocket Use Cases

1. What are common use cases for WebSockets?
2. How do you implement a real-time chat application using WebSockets?
3. How do WebSockets power online gaming applications?
4. What is the role of WebSockets in real-time stock market updates?
5. How are WebSockets used in collaborative editing tools like Google Docs?
6. Explain how WebSockets can be used in IoT applications.
7. What is the difference between WebSockets and MQTT in IoT?
8. How do WebSockets enhance video streaming applications?
9. What is the role of WebSockets in real-time dashboards?
10. How do WebSockets enable live auctions?

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Performance Optimization

1. How do you optimize WebSocket message payloads?
2. What is fragmentation, and how does it affect WebSocket performance?
3. How do you implement compression in WebSocket messages?
4. Explain the importance of heartbeat mechanisms in WebSockets.
5. How do you measure WebSocket connection performance?
6. What tools do you use to benchmark WebSocket servers?
7. How does latency impact WebSocket applications?
8. What is the role of protocol buffers in optimizing WebSocket communication?
9. How do you manage concurrent WebSocket connections efficiently?
10. What is the impact of network congestion on WebSocket performance?

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Advanced Topics

1. What are multiplexed WebSockets, and how do they work?
2. How do you implement WebRTC over WebSockets?
3. What is the difference between full-duplex and half-duplex WebSocket communication?
4. Explain the concept of WebSocket tunneling.
5. How do you design custom WebSocket protocols?
6. What is WebSocket fallback, and how do you implement it?
7. How do you implement dynamic room management in WebSocket servers?
8. Explain how WebSockets integrate with serverless architectures.
9. How do you design real-time notifications with WebSockets?
10. What are hybrid WebSocket architectures, and when would you use them?

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Testing WebSockets

1. How do you test WebSocket connections using Postman?
2. What is the role of mock WebSocket servers in testing?
3. How do you write unit tests for WebSocket handlers?
4. How do you test WebSocket connections for latency and bandwidth?
5. What tools are used for WebSocket load testing?
6. How do you handle edge cases in WebSocket testing?
7. How do you simulate network failures in WebSocket testing?
8. What is the role of automated testing frameworks in WebSocket testing?
9. How do you validate WebSocket message integrity?
10. What are the best practices for integration testing WebSocket applications?

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Future of WebSockets

1. What are emerging trends in WebSocket development?
2. How do WebSockets compare to HTTP/3 in real-time applications?
3. What is the impact of 5G networks on WebSocket communication?
4. How do WebSockets interact with edge computing?
5. What role do WebSockets play in decentralized applications (dApps)?
6. How does serverless WebSocket architecture change traditional patterns?
7. What are hybrid communication models in WebSocket applications?
8. How do WebSockets integrate with AI/ML-powered systems?
9. What is the future of secure WebSocket protocols?
10. How do you see WebSockets evolving with IoT and smart devices?

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Practical Scenarios

1. How do you design WebSocket APIs for multi-tenant applications?
2. What are best practices for logging WebSocket connections?
3. How do you monitor WebSocket traffic in production?
4. How do you implement fallback mechanisms for unstable connections?
5. How do you handle rate limiting in a large-scale WebSocket server?
6. How do you manage resource cleanup for closed WebSocket connections?
7. How do you design WebSocket communication for high-availability systems?
8. What tools do you use for debugging WebSocket applications?
9. How do you manage distributed state in WebSocket servers?
10. How do you implement end-to-end encryption in WebSocket applications?

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