Initial screening interview was done via a recruiter. They were desperate for people to fill roles is the impression I got. However, I wasn't able to join immediately or in the location they needed, so we terminated the process.

Detailed and intense interview process. Can take months, so don't get discouraged. First the recruiter will cover a number of questions ranging from general (why are you interested in Meta, what is your current situation, etc.) to more substantive related to the experience needed for the specific job. Then you may go through a series of 6-7 interviews. Then additional interviews may get tacked on. And it could be weeks to months after the last interview before hearing back.