There was an initial paper "pre-test" with some questions about technologies that you are familiar with. For example, "What programming languages are you most comfortable with?". The pre-test included 3 programming questions. The code could be written in 20 lines or fewer.
After passing the pre-test, I was given 10 days to take a timed, online "interview". I thought it was going to be a coding test, but it was not. There was some pseudo-code involved, but it was mostly asking questions like "Explain the difference between X and Y." "What problems do you see in the following code?" In my case, there were 12 questions. The time limit was 60 minutes. It seemed unrealistic to be able to answer all 12 in 60 minutes. The test read "you don't have to answer all the questions", so I felt a bit of a relief. I was able to answer 7 questions thoroughly and a few briefly. Some of the questions were focused on client-side technology, some questions focused on server-side technology.
If you want to prepare for the online test, I recommend making sure you know basic algorithm concepts and can write pseudo-code (or real code, if that's faster for you) for hall-of-fame sorting, searching, and data structures algorithms. I didn't have to write a whole class for a binary search tree or anything, but you should at least know the high-level APIs of everything in a 200-level CS course at a university. There were some high-level questions about system design and scalability. I would also recommend knowing as much detail about how your "platform of choice" works under the hood. For example, if you want to be a Java engineer, you should know a good deal about the JVM and memory management.
I was offered a Skype interview after passing the online test. The interview lasted for 2 hours. During the interview, two engineers asked many follow-up questions about each of the online test questions. I recommend being able to talk at length about all of the online test questions. If there is a question about optimization, you should know some concrete examples of how to optimize your solutions.
Within 2 days, I was given a polite letter that said they would lot proceed with my application.
After reading some of the other reviews on Glassdoor, I'd like to make it clear that my experience was exceptionally professional and friendly. Once I have some more experience, I will certainly consider applying again. It seems to be a great team to be a part of.
