Yelp took a long time to get back to me. I applied through a referral process, and my contact mentioned to his recruiter that I had an offer deadline coming up, which sped up the process. I wouldn't expect to hear back sooner than a few months after applying if you don't have a referral.

Initial phone interview: A simple 20-minute HR interview.

Online coding screen: A short, easy coding question and 10 fast, knowledge-based questions. Definitely look at the other reviews on here to answer these. It's strange that they ask these questions because most of them are only testing familiarity with Unix.

Skype interview: I met with a really nice guy, and he asked me a difficult coding question. I couldn't come up with an optimal solution, but he was okay with me coding the naive version. I finished a working version of the naive solution and made it to the onsite.

Onsite: Four 45-minute interviews back-to-back. Stressful, but not impossible, and everyone I met with was great. They focus pretty heavily on knowledge-based questions: about Java garbage collectors, stack vs. heap questions, threading practices, some simple networking stuff, compression, encryption, and Android specifics. All very high-level, just to test your breadth of knowledge. I did very poorly on these. There were also four algorithm-based coding questions on a whiteboard, which I answered with optimal, working solutions.

Apparently, they put more weight on the knowledge-based questions, as I did not receive an offer. Overall, Yelp had a really organized, fast, and friendly interview experience. I was unprepared for the emphasis on knowledge-based questions.

There wasn't one difficult question, just a lot of random questions from all fields of CS.