I wanted to start by saying I will not share any specific questions. As sharing questions will not help anybody and I have signed the NDA

I have been practising a lot since September. Absolutely gutted to have been rejected. I wanted to write my experience as it might help others who are in the same boat as me. I did extremely well in System Design and Behavioural but it was the coding round which failed me.

YOE : 15 years
Location : London

Phone Interview 1
2 standard LC questions. The first one was slightly twisted and I got a bit confused.
Since I had done the second question really well and there were mixed signals, recruiter asked me to take another telephonic interview

Phone Interview 2:
1 String question and 1 Data structure question. Both were not from LC tagged list
I managed to code well and got selected for Onsite rounds.

I asked for 2 months to prepare

Product Design - I had opted for Product Design instead of System Design. Was asked to design a feature related to facebook website. I was quite confident and drove the entire conversation. Got positive feedback on this.

Behavioural - Standard questions. I was suprised as there was a coding question as well in the last 15 mins. Again got positive feedback on this.

Coding Round - 2 questions
1st question- very standard LC question - I had practised so many times. I still got a bit confused with the edge cases. Managed to code it up in the end

2nd question - this was not a standard LC tagged question. The interviewer gave me some hints and I managed to code it up but didn't have time to test.
Feedback - Standard was slightly below par to offer.

Coding Round -2 questions
question1 : Array related question related to pigeon hole principle. I had glanced this question a week before the interview. I didn't go through it detail as it could be solved in multiple ways.
Interview was not happy with my solution, he wanted it to be coded in the most optimal way

question 2: Another array related problem. Not in leetcode. It was confusingly worded. I solved it easily with O(n) space.
Feeback was I didn't code it in optimal way

I have spent every weekend leetcoding, listening to videos for problems I don't understand.
Worked through the problems after work. Took mock interviews , learnt the patterns.
It has been extremely taxing and I feel so bad to have given up my family time for this

Most of them who interviewed me had 5-6 experience in total. Facebook expects you to solve the questions in the most optimal way in the first try. Both the coding interviewers didn't bother to correct me or give me time to think for an optimal solution. Why ask me to go ahead with the code and give the feedback that it wasn't optimal?

I have so many years experience. I have brushed up my DS and algo skills as this is something I don't do it in my day to day job.

I got really tensed for the coding interview, that might have played a part in my failure. I really gave what it takes for the interview. Even took a week off to study. I could have spent the same time with my family.
Anyway I am going to take a break from FAANG for now

Thanks for taking time to read this.

My advice, don't rely on leetcode. Use it only as tool to test your knoweldge. Grilling LC won't help.

Update
Microsoft

I had 6 rounds of interviews in total including phone interview.
I really enjoyed the whole experience. It was from more experienced people including the director for the last round.

The interviews were slightly easier and relaxed compared to facebook. LC standard questions for coding and standard design questions

They focused more on my experience and what value I can bring to the team.