Optiver reached out to me after finding my resume online. It was a very quick process. I had a 30 minute behavioral interview, which felt very natural. After that, on the same day I was given a hackerrank which I had a full week to complete. The challenge was very doable and I had 24 hours to solve three problems which did take a few hours (not the usual one hour challenge; it was a "project" which I suggest you use your best coding practice on). After that, I was invited on-site. This consisted of four interviews - a code review of the hackerrank, a design interview, which was basically a technical interview but without coding, a behavioral interview, and an executive talk with the CEO and CTO. Overall, the experience was great. To be honest, I thought the behavioral interview didn't go great because my interviewer was very adamant about "only the best can get a job here" and you have to "be the best not to get cut". The whole process took probably only three weeks so props to Optiver because from my experience some companies take months even if their interested in you.