I got contacted from an HR through email to setup a phone interview, since I was in the US but the interviewer was in Singapore. The first phone interview was mainly about walking through resume, personal interest and goal, then we talked about the position, responsibilities, etc. After a few days, I got another email from HR to schedule 2nd round of interviews. There were 4 interviewers for this round. Because of the location and time difference, I had the interview through video conference, two interviews per day. The 3 interviewers were from the same team, the other one was from the other team. They were all nice and friendly. Most of the questions were case studies (both strategy and quantitative questions), e.g. how should a plumber advertise his business, estimate number of light bulbs in UK. About a week later, I got an email from HR saying I got through to the third round, the final round. This time it would be at Google office in the city where I lived in, through video conference to the person in APAC. I asked HR and she said the interview will be quite casual, catching up from last interviews. I was very surprised that the interviewer asked me more of case studies, which I wasn't (mentally) prepared for it. I knew when the interview was over that I screwed this up.