Entire process took about 2.5 weeks. Recruiter reached out to me, screening interview for 20-30 minutes. Explained that I have other offer letters expiring soon, Facebook accelerated their the interview process. Following week I had two 45 minute interviews back to back, the first going over a portfolio piece of mine in-depth, and the other critiquing an existing app (Yelp). Overall this interview process was surprisingly fun, and it's clear to me that Facebook cares about it's employees.

Straightforward like any big tech interview, but long and intense. Formats are pretty standardized so it just takes practice. Questions appear like it's from a bank, so if you're prepared you should be fine.