The interview process was approximately 3 hours. A con to the rotational interview is that each set of people ask the same questions about your previous experience and what you hope to gain. What I disliked is each would ask what do you like about optiver -or- are there any questions about the company. This redundant question was a little annoying because after I asked the first time I didn't need to ask again and it left the interview silent at the end. I would say overall the interview was fun and engaging. They have a "brainstorm" session in which you get to build a fictitious company and really showcase how you think. The last and final session is time spent with a CEO, which in itself is fun. Number 1 dislike is having more than one person across the table.