I was refered by my friend to interview for google, sorry I would like to not put too detailed information here.
My friend's team has a openning then he forwarded my resume to his boss, I spent 1 month to refresh myself for all kinds of algorithms, data strucutres, etc. I don't have a phone screen and directly jumps to the virtual onsite.

first round:
behavior questions, I just keep talking, no clue if I am doing good or bad, the interviewer don't talk much.

second round:
Leetcode easy level question, the interviewer is nice.
One thing is the question has no function signature to start with but leetcode problem has, actually the function signature is a big hint to the problem to solve, the interviewer corrected me and I can finally make up a solution. following up about parallelism, but is easy.
keyword: binary search

third round:
I didn't see the problem in LC, it takes me about 15 minutes to understand what really the interviewer is asking for, then I give a brute force and goes to O(n^3), then realize I can make into O(n^2), after the interview I found I can make it into O(nlogn), but I guess it should have an O(n) solution, my bad, I just can not give a perfect solution during the 45minutes.

I get great pressure during the this round, I guess this round is the reason why I failed. The interviewer talked nicely but brutle, he is not going to give any hint, I feel he just don't like me.
keyword: string/substring

fourth round:
system design, the problem is very long, but the solution is VERY easy.
The interviewer said I have a flaw in the code but I corrected him that it's C++ feature and his understanding is wrong.
He then asked me some very easy follow up.
keyword: FIFO

last round:
my friend's boss, she don't have any formulated problem, we just had a technical talk, during the talk she gives the project she recently working on and asked me for solution/suggestion, she said I have a good reputation as super strong when my friend refers me, and my solution/suggestion is almostly same that her team uses, I feel good during this round.
keyword: queue

if I need to give score to my self:
roudn 0: 75/100
round 1: 80/100
round 2: 50/100
round 3: 80/100
round 4: 80/100

The next day my friend's boss send him a message saying I am strong during the interview, and she hopes I would select her team to join. When I got this message I thought I have made it, but actually that's not true. The next Monday HR called me and said I failed, because of Google's policy he can not share the reason, and I can apply 1 year later.

It's a good experience of interview, I have worked 6+ years, this is my second onsite interview during my career, I gained some experience of interviewing.

Good luck to all of you guys.