WebSocket & Async APIs interview questions — Hard
75 hard-level WebSocket & Async APIs questions from our API Testing bank, each with the correct answer and an explanation of why it is correct.
This topic slice is available to practise but is not yet part of our indexed set.
What this covers
WebSocket & Async APIs appears throughout API Testing interviews. At hard level, interviewers are typically checking depth under pressure — edge cases, failure modes, performance characteristics, and the trade-offs you accepted. Work through these, then explain your answer out loud; the second part is what interviews actually test.
4 example questions
1. Regarding WebSocket, which of the following is a false statement?
- A. AsyncAPI is a load-testing tool, not a specification.correct
- B. Testing WebSockets involves validating connection lifecycle, message order, and reconnection behavior.
- C. A WebSocket connection starts as an HTTP request upgraded via the Upgrade header.
- D. AsyncAPI is a specification for documenting event-driven APIs, analogous to OpenAPI for REST.
Why: The selected statement is false. The other options are accurate statements about WebSocket.
2. Identify the INCORRECT statement about WebSocket:
- A. AsyncAPI is a specification for documenting event-driven APIs, analogous to OpenAPI for REST.
- B. Testing WebSockets involves validating connection lifecycle, message order, and reconnection behavior.
- C. Server-Sent Events (SSE) stream data one-way from server to client.
- D. WebSockets allow only the client to send messages, never the server.correct
Why: The selected statement is false. The other options are accurate statements about WebSocket.
3. Which of the following statements about WebSocket is FALSE?
- A. Message-driven systems are often tested by publishing to and consuming from queues or topics.
- B. Server-Sent Events allow the client to stream data to the server.correct
- C. Testing WebSockets involves validating connection lifecycle, message order, and reconnection behavior.
- D. AsyncAPI is a specification for documenting event-driven APIs, analogous to OpenAPI for REST.
Why: The selected statement is false. The other options are accurate statements about WebSocket.
4. Which statement about WebSocket is NOT correct?
- A. Message queues can only be tested with a web browser.correct
- B. Server-Sent Events (SSE) stream data one-way from server to client.
- C. Load testing WebSockets measures concurrent connection capacity and message latency.
- D. WebSocket provides full-duplex, persistent communication over a single TCP connection.
Why: The selected statement is false. The other options are accurate statements about WebSocket.