Very easy, two stages, second stage involved some more technical questions about your CV. But over all very easy interview process. Know your CV very well, and be able to explain projects and examples.
It was pretty simple. They asked me about data structures and how to use them for problem solving. I had a couple of behavioral questions as well around 'Tell me about a time when..."
My interviews were conducted remotely and sometimes were informal. I wish they had flown me out to interview at the headquarters. Apple sends a contingent of employees to recruit at my school each year, and that is where I got the job.