Had a recruiter screen, technical, then another technical and system design, but failed the system design. All the technical questions were easy, but the system design portion left me puzzled on what the interviewer wanted. The interviewer didn't want to go in-depth on technologies used, or wanted any discussion regarding architectural tradeoffs of using technologies after giving a working design. Not even deep dives were asked. I'm not sure what their grading criteria is, but it feels unfamiliar with system design interviews I've had.

I find it ironic that throughout the process, many interviewers insisted that the company has a very technical high bar, yet they have been using the same interview questions for the past 4 years. You would think if they had such a high technical bar, they could come up with new/more than one set of questions. I did very well on all 3 technical interviews (as I already had the answers) yet somehow did not move to the final round. I suspect it was my system design interviewer who gave me a "no hire" because unlike the 2 coding rounds, where I ran my code through many test cases and passed all of them, you cannot do this with system design. There is no objective way/machine to verify your answer. Also, he seemed annoyed and upset throughout the interview, almost like he didn't want to be there. Despite presenting a valid system design, I left this interview a little skeptical because of the interviewer's bad mood as well as the fact that he did not ask ANY questions or probe into my design at all. A normal system design would have questions like "how would you handle if we reach x DAU?" or "what happens if we start having bursts of traffic? How would you change your design?" None of that, just an angry face watching me. Overall, I had positive experience because I have nothing to complain about aside from not understanding why I didn't move forward. But perhaps if you get a different interviewer for system design or you get him on a day when he is in a better mood, this won't happen. I gave it very easy because the answers are all here in this thread.