Why Old Mission Is Worth Your Attention
Old Mission Capital was founded in Chicago in 2008, in the middle of the worst market dislocation in a generation, and built its business on a single idea: exchange-traded funds were becoming the plumbing of modern markets, and someone had to keep their prices honest. Nearly two decades later the firm is one of the more respected ETF market makers in the world, reportedly employing a few hundred people across Chicago, New York and London, with a European presence that has grown steadily since Brexit reshaped where ETF flow gets priced.
Most students who can name Jane Street, Citadel Securities and Optiver have never heard of Old Mission. That is partly deliberate. The firm trades its own capital, has no outside investors to court, and does almost no marketing. But for candidates targeting proprietary trading, it belongs on the list: the interviews are hard but humane, the desks are small enough that juniors get real responsibility early, and the ETF specialisation means the work is genuinely differentiated from the options-heavy Chicago crowd.
This guide covers what Old Mission actually trades, the roles it hires for, the interview process stage by stage, the question types that come up, and honest compensation estimates for a firm of this profile. You can also see the Old Mission firm page on Quantt for a snapshot.
Old Mission at a Glance
- Founded: 2008
- Headquarters: Chicago, Illinois
- Offices: Chicago, New York, London (a continental European presence has also been reported)
- Size: Reportedly a few hundred employees
- What they trade: ETFs across equities, fixed income, commodities and currencies, plus the underlying baskets and related futures and options
- Speciality: ETF market making and arbitrage, including creation and redemption
- Roles they hire: Trader, Quantitative Developer, Software Engineer, Trading Operations
- Application route: the firm's careers page, or via the Old Mission firm page on Quantt
What Old Mission Actually Trades
ETF market making sounds narrow until you look at what it involves. An ETF is a wrapper around a basket of other instruments, and its price is tethered to that basket by arbitrage. When the ETF trades rich relative to the basket, a market maker can sell the ETF, buy the underlying constituents, and deliver them to the issuer in exchange for new ETF shares (creation). When it trades cheap, the trade runs in reverse (redemption).
Doing this well requires three things at once. You need fast, accurate fair-value models for the basket, which is hard when the ETF holds 2,000 bonds that trade by appointment or foreign equities whose home market is closed. You need execution across every venue where the ETF and its constituents trade. And you need inventory and risk management, because between the trade and the creation or redemption you are warehousing exposure.
That last point is why ETF market makers care so much about correlation and hedging questions in interviews. The core skill is not spotting the mispricing; it is knowing what you are actually exposed to while you hold the position. Our market making guide covers the general framework, and the ETF case is one of its most instructive applications.
Old Mission is a registered market maker and authorised participant across a wide range of ETF issuers, and reportedly quotes thousands of ETF lines globally. The firm is closer in spirit to Flow Traders and Jane Street's ETF desks than to the options market makers that dominate the Chicago scene.
Culture and the Shape of the Firm
Old Mission is small relative to its footprint, and people who have worked there describe a flat, collaborative desk culture. Traders sit with developers. There is no research tower producing signals for a separate execution team; the person who notices an opportunity is usually close to the person who codes the response.
Two practical consequences for candidates. First, communication matters more than at larger firms. In a 20-person office you cannot hide behind a process, and interviewers select for people they want to sit next to. Second, generalists do well. The firm reportedly rotates attention across asset classes as opportunities move, so a fixed-income ETF specialist who refuses to think about commodity ETFs is less useful than someone who enjoys the whole surface.
The firm has also been named in "best places to work" style rankings in the trading industry press over the years, which is weak evidence on its own but consistent with what candidates report: reasonable hours by prop trading standards, low turnover, and little of the tournament culture found elsewhere.
Roles and What They Involve
Trader. Watches markets, manages inventory and hedges, prices creations and redemptions, and works with developers to improve the automation. Junior traders start on a desk supporting senior traders and typically take ownership of specific products within the first year or two.
Quantitative Developer. Builds and maintains the pricing, execution and risk systems. The stack at ETF market makers is typically C++ for the latency-sensitive path and Python for research and tooling; Old Mission job postings have historically followed that pattern. This is a role where C++ interview preparation pays off directly.
Software Engineer / Infrastructure. Networks, market data, exchange connectivity and internal platforms. Less trading-specific knowledge required at interview, more systems depth.
The Interview Process
Old Mission's process is shorter than the giant firms' pipelines. Candidates typically report three stages over two to five weeks.
Stage 1: Online Assessment or CV Screen
Trader candidates usually face a timed test of mental arithmetic and probability, in the same family as the Optiver and Flow Traders assessments: 60 to 80 arithmetic questions at speed, then multiple-choice probability and expected-value problems. Developer candidates face one or two algorithmic problems, or go straight to a technical phone screen.
Stage 2: Phone or Video Interviews
One or two calls of 45 to 60 minutes. For traders: probability, expected value, quick estimation, and a market-making game (more on that below). For developers: live coding, data structures, and language questions, with C++ depth for the low-latency roles.
Stage 3: Onsite
A half day in Chicago, New York or London. Three to five sessions mixing harder versions of the phone-screen material with desk-specific discussion: how would you price an ETF whose underlying market is closed, what happens to your hedge when a constituent halts, why might an ETF trade at a persistent premium. Expect at least one interview focused on fit, because small desks hire carefully.
Offers reportedly follow within one to two weeks. The overall bar is high but the process is less of a gauntlet than Jane Street's five-plus rounds.
Real Question Types
Mental Maths
Question 1: Quick basket arithmetic. An ETF holds three stocks with weights 50%, 30% and 20%, trading at 25 and $110. What is the fair value of one ETF share if the fund's divisor implies the basket price equals the share price?
Approach: 0.5 × 40 + 0.3 × 25 + 0.2 × 110 = 20 + 7.5 + 22 = $49.50. The point is speed and composure, not the arithmetic itself. Practise until two-decimal weighted sums take under ten seconds; our mental maths questions set is built for exactly this.
Probability and Expected Value
Question 2: The re-roll. You roll a fair die and can either keep the result in dollars or roll again and keep the second roll. What is the value of the game, and when do you re-roll?
Approach: The second roll is worth 3.5 in expectation, so re-roll whenever the first roll is below 3.5, i.e. on 1, 2 or 3. Value = (4 + 5 + 6)/6 + (3/6) × 3.5 = 2.5 + 1.75 = 4.25. Interviewers often extend this to two re-rolls; the threshold logic is the thing being tested. More of this style in our probability interview questions.
Question 3: Correlated legs. You are long an ETF and short its basket. What is your P&L exposure, and what could still hurt you?
Approach: In theory you are hedged, but in practice you carry basis risk: the ETF and the basket can diverge intraday, constituents can halt, the borrow on short legs can be recalled, and creation or redemption costs can move. A good answer names two or three of these and quantifies at least one.
Market Making Games
Question 4: Make me a market. The interviewer asks you to quote a two-way market on the number of windows in the building, then trades against you and asks you to update.
Approach: Start wide enough to reflect your uncertainty, size small, and move your quote in the direction of the flow: if the interviewer keeps lifting your offer, your estimate is too low and your market should move up. The evaluation is about process (width versus confidence, adjusting to information, tracking your position) rather than the final number.
Fit
Question 5: Why ETFs, why a small firm? Have a genuine answer. "I want to see the whole trade, not one slice of a pipeline" is credible if you can back it with something you have built or traded. Generic prop-firm enthusiasm reads poorly at a firm this size.
Compensation Estimates
Old Mission does not publish pay, and there is far less levels.fyi data than for the mega-firms. The honest framing is that mid-sized Chicago prop firms typically pay graduate traders and developers in these ranges:
| Role | Location | Year 1 base | Year 1 total (est.) |
|---|---|---|---|
| Graduate Trader | Chicago / New York | 175,000 | 325,000 |
| Graduate Quant Developer | Chicago / New York | 180,000 | 300,000 |
| Graduate Trader | London | £80,000 - £110,000 | £130,000 - £220,000 |
| Experienced Trader (3-6 yrs) | Any | 250,000 | 1M+ |
Bonuses are discretionary and driven by desk and firm P&L, so year-to-year variance is real. Senior traders at successful ETF desks can reportedly earn well into seven figures in good years, but the distribution is wide. For context across the industry, see our prop trading firms guide.
A Four-Week Prep Plan
Week 1: Arithmetic under time pressure. Daily Zetamac or equivalent, plus weighted-average and percentage drills. Target consistent accuracy above 95% before pushing speed.
Week 2: Probability and EV. Work through dice, card and coin problems until threshold and conditioning arguments are automatic. Zhou's A Practical Guide to Quantitative Finance Interviews, chapters 1 to 4, remains the standard text.
Week 3: ETF mechanics and market making. Understand creation and redemption, premium and discount, tracking error, and what an authorised participant does. Then run mock market-making games with a friend: quote, get traded against, update, and review your position afterwards.
Week 4: Mocks and firm knowledge. Two full mock interviews under time pressure. Read what Old Mission says publicly about itself, and be ready to explain why ETF market making specifically, not prop trading generally.
Developers should substitute weeks 3 and 4 with algorithm practice and C++ depth: memory model, move semantics, and the standard data-structure repertoire.
Where This Guide Falls Short
Old Mission is private and quiet, and that limits what anyone outside the firm can verify. Headcount, office footprint and desk structure are drawn from public reporting and candidate accounts, both of which age quickly. The compensation table above is an estimate band for firms of this type, not firm-specific data, and the interview process varies by role, office and year. Treat everything here as a starting map, and treat the firm's own recruiters as the source of truth on process.
Compensation & recruiting notes
Pay ranges in this guide are illustrative estimates from publicly discussed bands and anecdotal reports for comparable firms - not official figures from the employer. Packages vary widely by desk, office, performance and year. Hiring processes change; nothing here guarantees an interview, assessment format or offer.
Frequently Asked Questions
What does Old Mission Capital do?
Old Mission is a proprietary trading firm founded in Chicago in 2008 that specialises in ETF market making and arbitrage. It quotes ETFs across asset classes, hedges with the underlying baskets and related derivatives, and uses the creation and redemption mechanism to keep ETF prices in line with fair value.
How hard is the Old Mission interview?
Demanding but shorter than the largest firms' processes. Expect a timed maths assessment, one or two phone rounds of probability and market-making games, and a half-day onsite. The bar on mental arithmetic and expected-value reasoning is comparable to Optiver or Flow Traders.
Does Old Mission hire graduates and interns?
Yes. The firm reportedly runs small graduate and intern classes for trading and technology, concentrated in Chicago and New York with some London hiring. Class sizes are much smaller than at Citadel Securities or SIG, so timing and persistence matter.
What programming languages does Old Mission use?
Job postings and candidate reports point to the standard prop-trading stack: C++ on the latency-sensitive path and Python for research, tooling and analysis. Trader candidates are not usually tested on programming, but comfort with Python is increasingly assumed.
How does Old Mission compare with Jane Street or Flow Traders?
All three are serious ETF liquidity providers. Jane Street is far larger and runs a famously long interview process; Flow Traders is Amsterdam-centred and listed, so its economics are public. Old Mission sits between them in visibility: private, mid-sized and Chicago-rooted. See our Flow Traders interview guide for the closest comparison.
Can I move from Old Mission to a hedge fund later?
ETF market making experience travels well. Skills in fair-value modelling, execution and inventory risk map onto systematic funds and other market makers, and mid-sized prop firms have historically been a common stepping stone in both directions.
Practise the questions Old Mission Capital: Careers & Interview Guide 2026 actually asks
Reading about the interview is one thing - sitting one is another. Quantt's interactive coding tests are modelled on the same problem types that show up in firms like Jane Street, Citadel, Hudson River and Optiver. Run real Python in the browser, get instant feedback, and benchmark yourself against the bar.
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