Initial phone screen with prospective boss. Two coding interviews on coderpad. First chatted about research for most of the call and didn't get much time to code, second spend the entire time on a coding exercise. The question in the second was a CS algorithm question, rather than anything related to statistics or coding per se -- it could have been done in pseudocode. The process seems to be designed to weed-out people without formal CS training, though I didn't get the impression that writing low-level code was an important aspect of the job. If you really want to work at facebook core data science, you should probably study algorithms so that you'll have seen what they're going to come at you with before they do.

7 Interviews, didn't receive an offer after the final round. Time-consuming process, which includes multiple rounds of technical interviews (design, coding, behavior, etc.) and a 1-hour research talk. The team leader was unpleasant to interact with.