Meta Developer interview questions

Recruiter contacted me on Linkedin. I requested for in person interview in place of telephonic. Arranged a 1 hour interview at Menlo park office. Cleared the interview and was called for a six round interview. Interview was strange. Easy and not so complex algorithmic rounds. Not sure what is so special about those rounds or whether they were even part of the decision making. Interviewers were happy with the answers and not much corrections. Then there were these design rounds. One of the rounds was about designing location services. The interviewer was very knowledgeable. Pointed out my in-efficiencies with the choice of data-structure. Enjoyed it. Then started the real fun in the final round. An awesome interviewer with an awesome attitude. He spoiled my interview experience though. Asked me to design a messaging app system. Once the interviewer breaks the comfort zone, it would be a difficult place to stand. His expressions were horrible and sometimes I felt like saying "shut-up and listen first" which I didn't say obviously. When I mentioned that the server knows the ip address of client only when the server receives a packet from client. He said, there are a lot other ways it happens. I mentioned the only way is clients packet to the server. He made it an argument and finally I had to ask him to mention a way. He skipped the part and asked me to move on :-D Ignoring the final round, I actually enjoyed the interview process. No offer though :-)

I had two interviews and each takes 45 mins. I answered each smoothly and near perfectly. All bug-free code. But they still reject me without giving any reason or feedback.