I was invited to this interview after doing Google Foobar. The first-round technical interview was relatively easy. I had to code an answer to the following simple question, which I did in Python. Then, my interviewer asked me to do the same thing with Python iterators. I wasn't sure how they worked, so he taught me how they worked. I made an implementation that didn't quite work and we were over time, but it seemed as if he didn't expect me to code it right due to the time constraint (the interview was going over time, as it had taken some time for me to code the first problem and he had spent some time teaching me about iterators). My interviewer told me at the end that no one else had successfully that problem and that my explanation to the solution was very clear. Then, the process was extremely slow. I'm not really sure how these interviews are evaluated, but I got a call 5 weeks later (after following up thrice) that I was rejected. Then, I got an email on how to prepare for technical interviews, and the reason I was rejected didn't seem to be very clear. Maybe the comments my interviewer had made to Google were misinterpreted in such a way that the Google admissions people had thought I had a bad interview. And as a reference, I am in the third round of my Jane Street trading intern process, which is well-known to be way more difficult.