FB interview process is fairly open and transparent for the most part. I had following rounds - Recruiter screening, Phone interview w/ one of the TPMs, Loop Interview, and a follow-up interview for System Design, which is part of the Loop Interview. Loop Interview had 5 back-to-back 45-minute rounds - two of them were technical and rest behavioral and leadership assessment. Recruiters in most part work with you to help you prepare best for these interviews. They were mostly transparent with the process and feedback, but at the end not so much. After the final follow-up interview, they told me that I did really well and they were moving with final steps of exec review and getting the offer out to me, but after a week sent a note of no-offer with no explanation. BUMMER! However, I still believe their recruitment process is far better and transparent than any other in FAANG.