Meta Software Developer interview questions

I was referred internally by my friend. I attended a phone interview after contacted by a recruiter. The interviewer actually told me directly on the phone that I should work more on my coding skill. So I was totally surprised to learn that the interviewer's feedback was positive and they'll continue with my application. All the following process was mostly coordinated by another recruiter, who is very responsive and I greatly appreciate his help. The on-site interview had 2 sessions before noon and 3 after, with the last one and lunch time not being evaluated. Originally I was told that I'll hear the result the next week, but instead I waited 2 weeks and learned that I didn't make it. The recruiter did emphasize that I was really close, and also let me know that it was the system design question that I didn't perform well. (There was yet another coding question that I found difficult, but the recruiter told me that they had no problem with my coding skill.)