There are two 45 mins sections for coding interviews. Another simple coding problem in the behavioral interview round. If you prepare 200 Leetcode problems under the Facebook tag, you should be able to crush the coding problems. For system design and ML design, I think I did average on ML design and bad on system design. That's probably why I got rejection.
The overall interview process is good. The only thing I'm not happy with is the ML design part, there is no question asked on the ML fundamentals at all.