Overall it was an extremely pleasant process. Everyone was very friendly and helpful along the way, and every step was clearly explained. I was assigned a recruiter, Alan, who led me through the process, answered my questions, and even met me onsite which was nice.
The process consisted of a short screening by the recruiter where I was asked about my previous experience and education and was described the role in more detail. The next step was a phone conversation with the hiring manager. This was where I learned about the role in the most detail and I left the conversation feeling like I could really imagine my day-to-day role, my responsibilities, etc. This was very refreshing compared to other interviews I've done where the description of a role is very vague. Finally the last round consisted of 4 interviews, each 30 minutes long. I had to do two interviews through video conference as the interviewees were in the US, and two onsite interviews.
The process was fun but also quite challenging, in a good way! Everyone I spoke to was intelligent and passionate about their work. Unfortunately in the end, the position was given to another candidate but I was not deterred! After speaking with everyone, and seeing the office, etc. it has only confirmed my desire to work at Facebook, and I will most definitely be applying to more roles here.
One critique I would make is that for a technical role, I felt that there should have been more questions that tested my technical abilities, e.g. more coding questions. I know some people won't like that but I think it's good to see if you have what it takes!