Status: Employed, YoE 10 years
Position: Senior Software Engineer (Non FAANG)

I was contacted by the recruiter via linked-in first for US position for which nothing happened, then another recruiter called saying he is taking over, and would want me to try for London.

Phone Screening (Jan) 45 Mins:
2 Coding problem.
* https://leetcode.com/problems/nested-list-weight-sum/
* Matrix each row containing 0/1 sorted, Find the smallest column having 1 (O(mlog(n))

Got confirmation within a week. My recruiter was very nice. He transitioned me to next level recruiter at London Office.
I got invitation for onsite, started my VISA process etc, but then COVID struck the world, I was not too confident then about cracking it, but was looking forward to free trip to London.

Few days before I was supposed to travel, I asked the recruiter about the COVID situation, and on the contrary I actually told them I am hesitant to travel for onsite looking at the situation. And next day I received an email from there senior recruiter/manager that they are canceling all onsite interviews, and changing them to video conf.

It was good and bad, good was I didn't had to risk for onsite and bad in two ways, I thought my chance free London trip is gone and on top of it, video interviews are tough, its difficult to gauge the interviewer on a video call. Though my initial round was not too bad.

Any ways, I went on to the Video interviews in same schedule, except I had to attend from home, I made sure of a good internet connection. Also FB reimbursed reasonable amount for the whiteboard, yes the system design interview was suppose to happen on video, super difficult.

Video Conf Interview(March):
NDA applicable so I wont put the questions but will add some details. All interviews were 45 mins. All FB employees then were WFH, so to save same the bandwidth interviewers were keeping the video off. Well it was bad, but there was no choice. Luckily the behavioral round happened with Video ON.

1. Coding Round: Leetcode medium FB questions, one was Matrix problem another was Binary Tree Problem.
2. Behavioral Round: One leetcode easier medium FB question at the end in 10 mins. Initial 35 mins were behavioral questions related to background etc.
3. Coding Round: One leetcode medium FB question, related to Binary trees. Another question I did not find in leetcode, it was a recursion problem, between medium to hard one.
4. System Design: Standard grokk-ing question, it was tough to do that on video but some how it went fine.

After its all done, I had OK feeling about the interviews, may be due to the fact that I could not gauge if the interviewer was fine with my solution and code. But apparently it went well.

Few tips which I followed:

• Ask question, might not be relevant at first, but could be.
• Be it a coding round or SD, start with a basic solution, there would be a bruteforce way to solve. Talk about complexity. If interviewer has not provided the a good sample i/o, make one before starting.
• Build on the bruteforce solution, give a best optimized solution. Talk about complexity.
• You could ask interviewer if he/she is fine with the approach, if they are fine, they will let you write code for it. Don't start to write code until interviewer is convinced with your solution.
• Keep talking through-out the process, as per them its important for them to know your thought process.
• Go through the prep guide which recruiter will share, also available in FB's career site, it turned out useful to me.
• Doing FB mock tests in leetcode helped me to prepare.

Since coding questions could be something you would have solved in leetcode don't get excited and give a optimized solution upfront, always build ground up, that's the key.

Though its hard to accept but leetcode FB questions are good enough prep for coding round.
grokk-ing the SD interview is good enough for SD interview.

Finally I got confirmation in 8 days, all interviews went well, unanimously they decided to roll-out the offer.

This post is a way to thank leetcode community. I have learned a lot from the process. Hopefully its helpful to other aspirants.