Process started with email from FB recruiter. It took around 2 months. They give you result almost immediately, I mean same day or next day.

First Interview:
Q.1) Finding longest sequence type something, easy question. It took few mins to code and dry run one/two inputs.
Q.2) Trie based questin. Interviewer made it two parts. First part was most important and second part if i can't code because of time as long as i can just explain the process should be fine.
I pick the perfect data structure and also coded second half of the problem. A little portion i just explained. Interview was saying code is perfectly structured and no issue at all.
Not sure why, they did another follow up coding interview.

Second Interview:

Q.1) Matrix related search based question. I offerred two solution. One is binary search on each row and another start searching from top right corner and progress toward the left side of the matrix. And then he asked me to compare both solution and I preferred diagonal search as it prunes the search space as it switch the row depending on the data set.
Eventhough I knew second solution works for granted and was best solution based on leetcode, still I asked him whether he likes it or not. Whether it will work or not. I think he wasn;t aware of that solution and said I;m not sure, may be we can see some code.
After I coded the solution, he gave 4 different input set to dry run. Program was correct and by this time we kind of ate up the time for second question.

Q.2) CPU Task scheduling, including question all together we had 5/7 mins. Couldn't complete the code.

He ate the whole time understanding first solution and punnished me the code clarity and code speed.

Got rejected eventhough questions asked were almost known.

Process is so intimidating. If you want to hire only world finalist competetive programmer, call them. Stop randomly searching linkedin and put some regular software engineers into this intimidating process pipelines and catch if they come out to be gold.