I applied online and got response from HR about 2 weeks later. The recruiter called for a brief background checking and asked a few basic conceptual questions, like time complexity of common algorithms. Then I was provided a online test link. The online test question is pretty easy. But you need to be careful and pay attention to corner cases, e.g. overflow. I screwed it up, because I misunderstood the problem. I didn't finish reading the whole problem and missed some requirement. I spent much time trying to find bug in my code. When I was pretty sure my code was right, I re-read the problem and then found the point I missed. At that time I was in a rush to modify my solution and therefore the code I submitted was kind of ugly.

Worst interview experience ever. Their founders came from Facebook, and I believe their whole company think they are as good as Facebook. The hr person was very impatient to my questions and the technical phone interview was the worst one ever. The one who interviewed me was yawning at all the time and I could hear he was typing and then he told me he was not listening to my answer. I don't know if he was working on something or was chatting maybe. And then he asked me to implement an algorithm. When I asked could I start coding, he said no, describe it first. When I described my solution, it turned out that he was not listening at all and was busy decorating his question in collabedit. He asked me to describe the solution orally twice before I could write anything. And I asked a question at last, it took him three times to finally understand what I was saying. The second day their recruiter contact me saying since i was not able to find a working solution, they are not able to move forward. I never saw any recruiter wrote a email like this rude and I'm very sure the solution I gave was absolutely correct. It just made me feel their whole company are jerks. Why you waste my time!