Well I am still trying to make sense of the questions that were asked and their relevance. As a web app developer you hardly use those things, they are pretty much baked in whatever framework you want to use. They asked questions as if they wrote a book on Spring Boot or Multithreading in general and were expecting a bookish answer. I tried answering the initial question on a topic, but the follow up question after followup is where I lost it. I gave up my enthusiasm after some time, and just answered in Yes or No. It is just as much a painful experience, maybe they are expecting an ex-FAANG employee to join the company.