Standard computer science/algorithms phone screen interview.
I've been a few years in my current job, and I have decided to try the job market again. My resume is impressive, I haven't padded it in any way, I've led software projects to release on time, and I'm finding it easy to get as far as phone screens, but no further.
This isn't a criticism of Facebook itself, rather of the whole Bay Area software engineering scene - since the last time I went for interviews, there seems to be a much bigger focus on getting the initial computer science/algorithms questions correct on the first go. Miss an edge case that the interviewer brings up, you're toast. Misplace a < instead of <= in an iteration, you're toast even if you find it yourself. Take longer than 20 minutes per question, you're toast. Try to recreate from first principles an algorithm you haven't thought about since you graduated, or never, ever used in your work, you're toast.
I've interviewed many people in my current job, and never regretted recommending employment to any of them. Every single one of the people I've recommended have made mistakes in their coding tests, and every one of them managed to find the errors when I pointed out that they had made a mistake. Perhaps I have lower standards, but when I interview, I look for how the interviewee recovers from a mistake, not that they are able to regurgitate something they learned from reading over Glassdoor interview questions.
Or maybe I just come across badly on the phone. Hard to say.
To recreate the process, go to leetcode and try some of the medium/hard exercises. If you can't complete it in under 20 minutes, and you have to redo some work to cover all the edge cases on submitting the solution, you can be sure that in an interview employers will thank you for applying, praise you for your impressive resume, and tell you no thanks.