Meta Sr. Software Engineer interview questions

I was contacted by a Facebook recruiter in Australia for a US position. Was scheduled a VC round within 2 weeks. The interviewer was from Instagram team. 5 minutes of introduction was followed by two data-structure questions for 30 minutes. I solved and wrote error-free code both the questions. After the interview when I checked solutions, my first algorithm was good but second one was not the lost optimized one. I guess that's where it didn't work well.

I had a loop with 4 interviews, one behavioral, two algorithm and one system design. The explained the problems clearly and they provided me feedback as I was explaining and working on the solutions.