Derivatives Foundation interview preparation

Questions

100

Traced to a firm

29

Firms

19

Updated

September 2026

Asked at

All firmsMSMorgan Stanley4Nomura4Akuna Capital2Amundi2HSBC2PIMCO2Bank of America1Barclays1Citadel1DRW1Goldman Sachs1Jane Street1Millennium Management1Mizuho1Old Mission Capital1RCRBC Capital Markets1Scotiabank1UBS1Wells Fargo Securities1

Topic

All topicsForwards and futures10Options basics8Option pricing7The Greeks10Volatility7Option strategies9Swaps and rates7Credit derivatives4Market structure and clearing6Indian derivatives8Trading and markets9Brainteasers6Fit9

Level

AnyCoreIntermediateHard

Type

AnyTechnicalCaseMarket viewBrainteaserFit

1. 096What did you learn from that experience that you hadn't expected to learn?FitIntermediatesuperdayJane StreetSales and Trading · London · 2026

   Say this

   Answer with something that genuinely surprised you, which means it should be slightly unflattering. The word 'unexpected' is the whole question — if your lesson is the one anyone would predict from the story, you have not answered it. The good version is a belief you held that turned out to be wrong.

   Then walk it

   1. The structure: here is what I expected going in, here is what actually happened, here is the belief I had to revise. Three beats, and the third one is the answer.
   2. Make the revised belief specific and about you. 'I expected the hard part to be the modelling and it turned out to be getting three people to agree on the assumptions' is a real lesson. 'I learned the importance of teamwork' is not.
   3. It is stronger when it is mildly unflattering, because that is what makes it credible as a surprise. Somewhere like Jane Street is explicitly testing intellectual honesty and the ability to update, which is the same trait as cutting a losing position.
   4. Then say what you did differently afterwards, concretely. An unexamined lesson is not a lesson. 'So on the next project I wrote the assumptions down and got them signed off before I built anything' closes the loop.
   5. Then, if it fits, name what you still find hard about it. Saying 'I am better at this than I was and still not good at it' is disarming and almost always true.
   6. And avoid the two failure modes: a rehearsed lesson that any story would produce, and a humblebrag where the surprise is that you were even better than you thought. Both tell the interviewer you are performing rather than thinking.

   Where candidates lose it

   Giving the predictable moral of the story. The word 'unexpected' means the lesson must be one you could not have guessed at the start, which almost always means it involves you being wrong about something. A generic teamwork or time-management lesson is a non-answer here.

   Expect next

   • What did you do differently after that?
   • What do you still find hard about it?
   • Tell me about a time you changed your mind about something important.

   Reported by candidates at Jane Street (Sales and Trading, London, 2026). Source: Wall Street Oasis.

2. 097What would you do if you get the offer?FitIntermediatesuperdayBarclaysSales and Trading · New York · 2026

   Say this

   Be straight about it. If this is your first choice, say so plainly and say why in one specific sentence. If you have other processes running, say that too and give your actual timeline. The question is a sincerity test, and an obviously over-eager answer fails it as badly as an evasive one.

   Then walk it

   1. If it is your first choice: say 'I would accept', then one concrete reason that could not apply to any other bank — a desk, a product franchise, a person you met in the process and what they said. Vague enthusiasm reads as a line.
   2. If you have a competing process: say so, name your timeline honestly, and say what would make the decision. Recruiters talk to each other and they can usually tell. Being caught in an easy lie costs you the offer.
   3. Do not negotiate here. This is not the compensation conversation, and treating it as one before an offer exists reads badly.
   4. It is also a legitimate moment to ask one good question back, because the answer changes your decision: which desk would I sit on, how does the rotation work, and who decides placement. That turns the exchange into a real conversation.
   5. The subtext is retention. Graduate programmes lose people to other offers and to the buy side, and they are trying to gauge how likely you are to be there in two years. Speaking about the medium term concretely — the product you want to learn, why that takes years rather than months — addresses that directly.
   6. And the thing that actually convinces: knowing something specific about their business. If you can say which of their desks you want and why, and reference something real about the franchise, the sincerity question answers itself without you having to protest.

   Where candidates lose it

   Over-promising with 'I would sign immediately, this is my dream job' when you have three other processes running. Interviewers ask this exact question to test candour, and they hear the rehearsed version all day. State your real position, including a competing offer if you have one, and be specific about why their business.

   Expect next

   • Where else are you interviewing, and how do we compare?
   • Which desk would you want, and what if you were placed elsewhere?
   • Where do you see yourself in three years?

   Reported by candidates at Barclays (Sales and Trading, New York, 2026). Source: Wall Street Oasis.

3. 098When would you use C++ over Python on a trading desk?FitIntermediatetechnicalWells Fargo SecuritiesSales and Trading · Charlotte · 2026

   Say this

   C++ where latency and deterministic performance matter — the execution path, the pricing engine inside a market-making loop, anything in the hot path measured in microseconds. Python everywhere else: research, calibration, backtesting, reporting and glue. Most desks run both, with the Python layer calling into C++ libraries.

   Then walk it

   1. The real distinction is the hot path versus everything else. If code runs a million times a second between a market data tick and an order, you need C++ or something comparable — predictable memory layout, no garbage collector pauses, control over allocation and cache behaviour.
   2. Python's cost is not just raw speed, it is the interpreter's unpredictability. A garbage collection pause of a few milliseconds is irrelevant in research and fatal in a quoting engine.
   3. Where Python wins decisively: iteration speed in research, the numerical and data ecosystem, and readability for code that a team has to reason about. Pandas, NumPy and the scientific stack mean a volatility surface calibration takes an afternoon rather than a week.
   4. The standard architecture is both. Numerical kernels in C++ exposed through bindings, with Python orchestrating. The heavy libraries you use in Python are C or C++ underneath anyway, so a vectorised NumPy routine can be within a small factor of hand-written C++.
   5. So the practical answer: write it in Python first, measure, and only rewrite the part that is actually the bottleneck in C++. Premature optimisation in C++ costs weeks of development time for latency nobody was going to notice.
   6. And I would be honest about my own level. If I am stronger in Python, I say that and say what I have done in C++ — knowing enough to read a pricing library and understand why it is written the way it is, versus being able to write a low-latency engine, are different claims and I would not blur them.

   Where candidates lose it

   Answering 'C++ is faster' and stopping. The interviewer wants the hot-path distinction, the point that most production stacks are both, and the discipline of measuring before rewriting. And do not overclaim your C++ — a technical interviewer will test it in the next question.

   Expect next

   • What specifically would you put in C++ on a market-making system?
   • How fast can Python get if you vectorise properly?
   • How strong is your C++, honestly?

   Reported by candidates at Wells Fargo Securities (Sales and Trading, Charlotte, 2026). Source: Wall Street Oasis.

4. 099Tell me about a time a position or a piece of work went badly against you.FitIntermediatesuperdayProp trading firmsSell-side sales and trading

   Say this

   Pick a real loss, state the size, and be specific about what your process got wrong rather than what the market did. The structure is: here was the thesis, here is what happened, here is the error in my process, here is what I changed. The error should be yours, not the market's.

   Then walk it

   1. Give a real example with numbers, even if small. 'I was long a position that was 30 percent of my account and it fell 40 percent' is credible. A vague story about a group project that got tight on time is not what is being asked on a trading desk.
   2. Separate the two failures explicitly: was the thesis wrong, or was the sizing and risk management wrong? Those have different fixes, and the ability to distinguish them is the actual skill being tested.
   3. Name the process error. Common honest ones: I sized to conviction rather than to the loss I could tolerate, I had no pre-defined exit so I kept renegotiating with myself, I added to a loser to improve my average, I confused a liquidity problem with a value opportunity.
   4. Then the change, concretely. A written thesis with a falsifier before entry, a maximum position size rule, a stop defined in advance, or a journal reviewed weekly. Say the rule you now follow and whether you have had to use it.
   5. Then the part that most candidates skip: what you did in the moment. Did you tell someone, cut, hedge, or freeze? Freezing is the honest answer for most people the first time, and saying so is far more convincing than a story where you acted perfectly.
   6. And no self-serving framing. Not 'the thesis was right, the timing was wrong' — that is the most common self-deception in the industry, and a trader hearing it will assume you have not actually learned anything. If the position was closed at a loss, the trade was wrong.

   Where candidates lose it

   Blaming the market, or the 'right thesis, wrong timing' framing. On a trading desk that phrase is a red flag, because it means you have preserved the belief that lost the money. Own a process error, name the rule you changed, and say honestly what you did in the moment.

   Expect next

   • Was the thesis wrong or was the sizing wrong?
   • What rule did you put in place, and have you had to use it?
   • What did you do in the hour after you realised?

Firm tags come from public, anonymous candidate reports on Wall Street Oasis: strong signal, not sworn testimony. Firms are named as the places a question was reported, not as partners of Fin Maverick. Answers are written for this page to show how to think out loud; they are not scripts to recite.