simple greetings, and the inteviewer briefly indroduced himself and what he do in facebook. Then he just throw out some product-related questions, with a bunch of follow up questions. Remeber to be well prepared for what you are saying, cuz the inteviewer may ask you why for some details, and you need also to make your thoughts well organized, since multiple reasons are required ( I think they expect the insights shown in your answer, not the generalized univeral truth). after that there is a sql task, not hard, but it seems that not a tiny mistake is allowed. They are not only looking at the correctiness of your answer, but evaluating your tech competence throughout the process. So, be confident. perform like a professionalist.