Hi,
Let me share my FB interview experience.
YOE: 12 years (7 years in tier 1 investment bank).

At the beggining of April I was contacted by recruter, even though I didn’t plan to change my work, I decided to try.
I took 3 weeks preparation for Phone interview, and 3 weeks for Virtual Onsite. In total solved around 300 problems (mostly medium and FB tagged).

Phone screen:

• 2 mediums. Nothing interesting happened.

Onsite:

• Round 1 and 2 (Coding): 3 mediums and 1 easy. The most diffucult here is that I was constantly speaking: what I'm doing, what case I'm testing, what also can be improved. And I didn't have enough time to think. Anyway I managed to solve all 4 problems and cover edge and base cases.
• Round 3 (Behavioral): pretty standart questions.
• Round 4 (System Design): not from *** System Design Interview. Here I didn't have enoght time to cover high level tradeoffs.

In 3 days I received rejection call from recruter. All 4 rounds feedbacks were positive, but I didn't convince behavioural and system desing interviewers that I'm senior developer and they considered me as E4.
From my perspective I mixed up priorities:

• In System Design I was speaking mostly about low level compontents and dataflows and didn't have time to discuss high level design.
• Also for behavioral questions I didn't point well the cases which show my leadership abilities and proactivity.

Hope it will help others to avoit mistakes I did.