Recently I got rejected from facebook virtual onsite. Here is my interview expereince, my preparion and tips for the interview:

YOE: 1 year experience
Position: Enterprise Engineer at Facebook
Location: London, England

Interview experience:

Due to coronavirus, the interview was taken virtually. All four steps of onsite interview - 2 coding interview, 1 Systtem design, and one Behavorial interview are taken over bluejeans app in a single day.

• Coding 1: Generally all Facebook coding interview sessions consits of two problems, interviewer gives an easy/medium level question and one medium/hard level question. Both of my coding round consists of two problem. In round one:
  Problem 1: https://leetcode.com/problems/find-all-anagrams-in-a-string/
  Problem 2: Very similer to Merge K sorted Lists. I have completed both tasks in time handling the edge cases. Interviewer seems satisfied.

• System Design: I have practiced *** the System Design interview and some youtube videos of basic system design concepts, that helped me a lot. It was not an excelent interview, but not bad also. I talked most of the times and discussing. I think thats the key to pass the system design round.

• Coding 2: This round also consists of two problem.
  Problem 1: I forgot the first one, but it was an easy string related problem, solved it within 15 minutes.
  Problem 2: https://leetcode.com/problems/alien-dictionary/. Completed this problem also in the given time and this interview went well I think.

• Behavorial: This is the round where I messed up. Interviewer asked some very commmon questions like "what are your greatest achievements/failures", "why do you want to join facebok" and some basic situation and conflict related questions. I haven't prepare solid answers for these types of questions before the interiew. Also the interviewr goes too deep into my projects written on resume. I answered them, but had a feeling that interviewer is not properly satisfied.

Got rejection mail after a week. In feedback phone call, recruiter said that I did very well in the coding interviews, passed the system design interview also, but the behavorial interviewer thinks I am not "Culturally fit" for facebook yet. That was the deciding factor in my case. Recruiter also told that it was a very close call and insisted that I should reapply after the cooldown period(1 year).

Interview preparation and tips:

Before the phone screen interview, I have already solved 550+ problems in leetcode.(I was rejeceted from Google Onsite earlier this year also, solved them for taking preparation for google onsite). So I started solving frequent problems of facebook again. For facebook interview, most of the problems are common from facebook tag in leetcode. If you have a facebook interview scheduled, I suggest to must buy leetcode premium for at least a month. (This suggestion is also applicable for google and amazon candidates also). Also I solved some easy problems to improve my coding speed. Remember that you have to solve a hard leetcode problem in 20 minute, your code must be fast, accurate and optimal. Last suggestion for facebook interview is that if the problem is common to you and you know the optimal solution, don't waste a second and start discussing the optimal solution.