The interview involved solving algorithm problems at a computer with the interviewer. I could use whatever language or environment I liked. There were 4-5 problems to solve, of varying difficulty but mainly graph mutations (read a tree, do some operation, emit a tree). It would have been really hard if I didn't know my stuff.

Immediately following that was a system design problem about how to build a big distributed system to solve a task. This was followed by a general conversation where I presented something I had worked on in the past.

Implement an algorithm for Secret Santa.