Old Mission Capital Interview ProcessTier 3
Old Mission: Chicago-based proprietary trading firm and ETF-focused market maker (also options). Online assessment, then technical rounds on probability, expectation and mental math, plus ETF, options and market-making questions (traders) or clean coding (engineers). Interviewers run live market-making games; the bar is fast, accurate probabilistic reasoning and trading sense.
Online Assessment
Old Mission's screen splits by role. The Quant-Trader OA is a fixed 35-question multiple-choice speed test - 25 minutes, the same questions in the same order for every candidate - heavy on probability, counting, expected value, and conditional probability / Bayes. The software track is a Codility-style set (mixed CS multiple-choice plus 2 coding problems, often a recurring JSON-string parser). Passing the OA leads to a behavioral round, then an onsite (game-EV brain teasers and market-making mental math for traders; C++ / systems for SWE).
Practice this round 46 problems ProA fixed, ordered 35-question multiple-choice bank done in 25 minutes (about 43 seconds each) - identical for every candidate. It is pure mental speed: P(sum), handshakes, widget / card EV, two-jar same-color, Bayes (double-headed coin, unsafe driver), pattern races (HH-before-TH, HHH-before-TTTT), and Markov tails (candy belt, donut box). Practice the recovered bank below against the clock.
Take the timed assessmentReal reported OA questions, on the clockProThe SWE / New-Grad OA is a Codility set (mixed MCQ + ~2 coding). The recurring coding problems below are auto-graded.
Smallest Integer Greater Than N With No Two Equal Adjacent DigitsThe answer is the smallest valid number that is at least . Start from the digit string of and scan left to right keeping the longest already-valiBalanced String SplitScan once and keep a running balance ( for `'R'`, for `'L'`). Whenever the balance hits , the run since the previous zero is balanced and can be cutLongest Lexicographically Smallest Palindrome From Two Pooled StringsA palindrome is fixed once you choose its left half plus an optional center, because the right half is forced to be the mirror of the left. To make it as LONG aSatisfy Customers By Opening At Most 2 ShopsBecause each list has only a few items, the natural move is to compress every shop and every customer into a bitmask over the small universe of item ids that acsee all 9 problems →The QT OA sometimes pairs the math bank with a short coding problem. Auto-graded below.
Array Challenge (left-comparison counter)Each left element contributes a signed amount whose magnitude is the gap to `arr[i]` and whose sign is positive when the left element is smaller. Note `+|arr[i]JSON Parser (nested lists of strings)This is a textbook recursive-descent parse over a tiny grammar with two productions: a value is either a string or a list, and a list is a bracketed, comma-sepaThe first stage is on us — you're seeing it in full. Unlock every later round, the must-do problems, and stage-by-stage prep across all 56 firms with QuantVault Pro.
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Old Mission Capital round-by-round guides
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Stage guides for every firm: superdays · behavioral questions · market-making games
Old Mission Capital interview — FAQ
What is the Old Mission Capital interview process?
Old Mission: Chicago-based proprietary trading firm and ETF-focused market maker (also options). Online assessment, then technical rounds on probability, expectation and mental math, plus ETF, options and market-making questions (traders) or clean coding (engineers). Interviewers run live market-making games; the bar is fast, accurate probabilistic reasoning and trading sense. The loop runs 4 stages: Online Assessment, Probability & Mental Math, ETF, Options & Market-Making Round, Onsite - Hardest Rounds.
How many rounds does Old Mission Capital have?
4 stages in total, starting with the Online Assessment and ending with the Onsite - Hardest Rounds.
How do I prepare for the Old Mission Capital interview?
Work the stage notes above, then drill the Old Mission Capital interview-questions set and the Old Mission Capital online-assessment practice — each problem has a full worked solution.