K · Interview Questions: This tab is the **interview exam** version of everything you built (Java/Spring, Express, NestJS) and tested (DevTools, Swagger, Postman, REST Assured, P
This tab is the **interview exam** version of everything you built (Java/Spring, Express, NestJS) and tested (DevTools, Swagger, Postman, REST Assured, Playwright) on this page from A to J — an interviewer does not ask "what is X?", they ask "you saw this in production, what do you do?", just like someone who lived through B1's missing `starter-validation` or F5's "code is right, doc is old" scenario. These 50 questions are based on the REAL defects and decisions you saw throughout the page; instead of memorizing, if you remember the mechanism BEHIND each question (why this bug happened, where the tester caught it), the answer comes naturally.
🎬 Interview Layers: API vs UI Testing
Interviewer: scenario question
API layer: the truth
The interviewer does not ask "what is an API?" — they ask "everything looks normal in the UI but there is a bug, how do you find it?". What they measure is layer thinking, not memorization.
A weak candidate looks at the UI screen: "no error on screen, no problem." This is the trap of trusting the text the UI shows (GROUP E).
A strong candidate bypasses the UI and drops down to the API layer directly: does `POST /api/v1/bugs` with an empty title return 201 instead of 400? The truth is hidden here.
The API layer reveals the defect: the developer forgot the `@Valid` gate from B6, and the UI's JS check was hiding this gap. The root cause is found.
The lesson — a strong answer names the layer: "the UI validates but the server has no `@Valid`; this is the Bean Validation counterpart in Java. I prove it by sending an empty title in Postman." Layer + root cause + Java = full marks.
The Order for Building an Interview Answer
Concretize the scenario…
Picture the question as "which endpoint, which layer, which symptom" in your mind.
Connect the root cause…
Connect back to a group (B-J) you saw on this page: where did the same pattern appear before?