I applied online. The process took 1 week.
Got sent a HackerRank Online Assessment very quickly. It consisted of one coding challenge (medium-ish) and one "IQ" test, in the form of a mini-game that tests your thinking speed and reflexes.
The following metrics were computed from 16 interview experiences for the Optiver Software Engineering Intern role.
Optiver's interview process for their Software Engineering Intern roles is very selective, failing most engineers who go through it.
Candidates reported having very good feelings for Optiver's Software Engineering Intern interview process.