Meta Developer interview questions

I was contacted by the recruiter who found me via graph search, and was asked whether I was job hunting. I chose to go onsite for the initial phone screen. The question was straightforward with emphasis on fast and accurate coding, and the interviewer was very knowledgeable. A few days after the screen the recruiter scheduled an on-site with me, and the dates were quite flexible. The on-site consisted of four interviews, 3 pure coding (of which one is about design) and 1 research interview (I guess this is for all PhD applicants). I was quite happy with the coding ones but the research one was, well, a little annoying since the interviewer seemed to be dismissive to everything. But overall, it was a nice experience, two interviews plus lunch + tour around plus two in the afternoon, and it was done! I did wait for 3 weeks till the decision was make, and during the period the HR seems to be a little nonresponsive. When I followed up what I received was something like a one line email saying "we are reviewing your case and will come back to you soon". This was a little annoying especially the feeling of being silently rejected started to grow, but I guess it is not the HR's fault anyway. In the end I was offered a job with flexible titles - software engineer or research scientist or whatever. I decided not to take the offer in the end, but the interview process was very smooth.