The first part is to pass a mental math online test that takes a couple of minutes. The test really isn't that hard. I didn't prepare as much as I should have but I think that if you prepare enough it's not bad at all. I got a borderline passing grade to move on to the next round. My first interview was a standard behavioral phone interview with somebody from HR who was really nice & was very conversational. She asked me to go over my resume & my experiences, why Optiver, what are your 2 strongest and weakest skills. As soon as we were wrapping up she said I would proceed to the second round of interviews which was a technical interview. The 2nd round was all technical and it's easily the most difficult interview I've ever had. I prepared by looking up mental math tricks, studying brain teasers & learning more about derivatives but all the preparation was for nothing as it didn't really help out. The beginning was a formal go over your resume & why trading & not something else. Then the interviewer started me off with a brainteaser which wasn't hard but I messed it up. Just to let you know the interviewer really emphasized accuracy & speed, which made me nervous. You also have to give an estimation for how confident you are about each the answers you give. Then I had a game where I had to make exact amounts using 10 dimes, nickels & quarters where again I messed up some amounts because of the time pressure. The easiest part was where he would give me a number and I had to give it's highest multiple. Overall this round went horrible for me. I wasn't really expecting to get that much pressure about answering so quickly. It went so bad that the interview lasted less than 15 minutes when it was supposed to go for 30-45 mins. In my opinion this job this really geared towards those who are naturally strong quantitative people. I'm a math major, which is probably why they chose to interview me, but I'm really the type that takes some time to get the correct answer. Those types of people who can answer brain teasers and hard mental math questions, such as 5437*3419, in seconds, are really what Optiver is looking for. I can't stress enough how much the interviewer really wanted answers as quick as possible.