I was already a Microsoft employee and applied to work with a team in another department. I spent a day in an interview "loop," where I was given a schedule. Each hour, I met with a different employee in their office to be asked one or more coding or engineering questions, which I would answer on a whiteboard (or verbally).

Some questions were more about writing a block of code, others were about answering abstract questions, such as "How would you accomplish X if given limits Y and Z?"

Given a block of memory, how would one implement their own heap memory allocation API?