3 rounds, different engineers with technical questions. They want to know your thinking process in the interview. You have demonstrate what you understand and show them the logics behind it.

i had my interview today and was asked the same question. also similarly, the interviewer had no sense of humor. it was not a enjoyable experience because i think i gave like 3-4 different ways of making a cantilever, but i was asked "what else?" like 10 times for the cantilever problem alone. i also have 7 years of work experience, but there was 0 question asked about it.