I first did a phone interview, in which I was asked to design the file system behind their index.

Then, in my first in-person interview, I was asked various typical Interview 2.0 style questions. It seemed very focused on 'how fast can you find the clever solution to this problem'. I answered questions in C and Java, mostly very basic data structure manipulation questions (implement a stack using a queue, collection of collections, etc.). The most interesting question I got asked was how to do the backend for Facebook.

A second callback interview was supposed to focus on design, but wound up asking me very similar data structure questions because the senior interviewers I was supposed to meet with were not available, and I got junior engineers instead.

Design the back-end for Facebook.

Design an iterator for a collection of collections in Java. The iterator should hide the nesting, allowing you to iterate all of the elements belonging to all of the collections as if you were working with a single collection.