4 for the coding challenge, 1 for the tech screening and 3 design question for the onsite interview. Sorry but I can’t recollect all.

The key in these questions is to cover the fundamentals, and be ready for the back-and-forth with the interviewer. Might be worth doing a mock interview with one of the Fitbit or ex-Fitbit Firmware Engineer experts on Prepfully? They give real-world practice and guidance, which is pretty helpful. prepfully.com/practice-interviews