I was referred and had a recruiter reach out about a week later. I scheduled a call with the hiring manager and asked in advance what this call would consist of. I was told that it would just be a resume review. When I got on the call, I was asked how well I knew some of the optional requirements and then asked a leetcode hard with only about 15 minutes left. However, it was one I had seen before so I was able to give correct answer. After that I spoke with the HM for well over the time limit about the job and their personal experiences working for MS. I was almost certain I was going to be moving forward since I really enjoyed the chat I had with the HM and was able to solve the question even though I was asked it by surprise. The only thing I can think of is that I didn't know some of the optional requirements that well. In that case then I think they should have been required instead of optional, to not waste anyone's time. I was also ghosted until I followed up multiple times .