Senior Staff Engineer applicants have rated the interview process at Apple with 3 out of 5 (where 5 is the highest level of difficulty) and assessed their interview experience as 100% positive. To compare, the company-average is 64% positive. This is according to Glassdoor user ratings.
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Multiple rounds - intermediate difficulty. Lots of procedural questions in the final couple rounds. Got the job after a few days after the final round with the hiring manager, where I presented a case study showing how products could be improved with respect to what i'd seen at competitors.