The entire process consists of four steps: 1) Answering questions on a company's page 2) Skype interview 3) Home task 4) Interview at the office On skype interview we discussed Objective-C, blocks, memory management. The home task was to build simplified analog of Yandex.Disk client for iOS. Offline interview took approx 6 hours and we discussed a bunch of topics of entire computer science theme (algorithms, design patterns, multithreading, iOS platform, ...) It's hard to remember any particular questions because it took place couple of years ago. In general, you should have strong knowledge in every topic mentioned earlier.