What candidates report
The firm publishes its culture and openings rather than an interview process, so this page is candidate reporting throughout and is hedged accordingly.
Candidates commonly describe a short introductory call covering background, motivation and logistics, followed by an assessment mixing brainteasers, probability and statistics, and coding, then technical rounds, then a longer day of back-to-back interviews.
Two features come up repeatedly and are worth preparing for specifically.
The engineering rounds are reported to be genuinely low-level. Candidates describe being asked to implement standard-library containers by hand - a hash map, a deque with correct iterator-invalidation behaviour - rather than solving puzzle-style algorithm questions. That is a different skill from competitive programming and rewards different preparation.
The trading rounds are reported to include live market-making games. Candidates describe quoting a two-sided market while the interviewer trades against them, and being expected to track their own position, profit and loss, and drawdown as it moves. Mental arithmetic, estimation questions and options reasoning appear alongside.
What to prepare
Quote, then manage the position. The reported market-making games are not arithmetic tests - they are about whether you know what you are holding after six trades and whether your spread reflects it.
C++ at implementation depth, for engineering tracks. Knowing how a hash map works is different from being able to write one.
Estimation and mental arithmetic. Both reported as recurring.
Practise the same formats
The question sets below are ours, written in the formats this process is reported to use. They are not Old Mission's questions, and nothing here reproduces any part of its assessment.