BS in CS at a top US school, 3.5 years of experience at unicorn tech companies, with decent engineering cultures. FB recruiter reached out to me in February, phone round March, onsite April.

Four rounds: system design, coding, personality, coding.

Systems design I heavily overprepared for, because at a previous interview at a FAANG I underprepared (thought it was a "how much do you know?" interview, did not read or watch tips, etc. and absolutely bombed).

Unfortunately I overprepared for a question like "Design FB" or "Deesign Twitter", when in reality it was like "Design Leetcode". I was caught off-guard; most of the time was spent thinking through the data types and tables, which was also worsened by the fact that I was on Google Draw. I thought I did terribly and afterwards thought I had no chance. I did some pushups right after, thinking that if I still had a shot I should keep my spirits up.

Both coding interviews were 2 questions; a short one and then a long one.

First was a simple tree traversal, then LRU cache, but once the recruiter knew I understood the solution he switched to another tree traversal question that I had never saw before, and had to solve with level-order traversal, basically BFS.

Second was simple string manipulations, then integer to english string.

Behavioral went really smoothly.

I was surprised I received an offer, I had mentally prepared myself that I got rejected. In retrospect I think I was being too hard on myself for my systems performance, given I was comparing myself to ppl who design incredibly complex systems really quickly. But I did well on the coding rounds so maybe that saved me.

I guess if I had any tip to give, it would be to not let yourself get sad or exhausted by one interview, keep fighting, keep your spirits up. I recommend exercising before you study, and exercising (push-ups) before and doing the interview so your body is in the same mental environment.