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QUANT INTERVIEW PREP · Flow Traders

Flow Traders interview prep

Flow Traders favours probability, trading intuition, and arithmetic speed.

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#042 · optimal_stoppingdifficulty 4

In the classical secretary problem, as n → ∞, what fraction should you reject outright before accepting the next best-so-far candidate?

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WHAT FLOW TRADERS FOCUSES ON

  • ·Arithmetic and mental math screens
  • ·Probability brainteasers
  • ·ETF and market-making logic
  • ·Trading-style estimation problems
  • ·Rapid structured reasoning

INTERVIEW OVERVIEW

Flow Traders is one of the world's largest ETF market makers, and the interview process reflects that focus. The early screens test arithmetic and basic probability; the later rounds pivot to ETF-specific trading intuition, market-making logic, and estimation under uncertainty. Candidates who pass typically combine three things: arithmetic fluency dialled up specifically for the mental math screen, a solid probability foundation covering the core brainteaser families, and at least conceptual literacy with how ETF market-making works (creation/redemption, arbitrage between ETF and basket, spread economics). Flow Traders hires almost exclusively into Amsterdam and New York; expect interviews to reflect the firm's Dutch-origin direct communication style. QuantPrep's probability and expected-value problems are directly relevant; for the ETF context, supplement with background reading.

INTERVIEW STRUCTURE

01
Online math test

Mental arithmetic screening. Timed, usually with decimals and percentages. Passing threshold varies.

02
Phone / video interview

Technical interview with a trader or researcher. Probability brainteasers, mental math warm-up, and often one trading-flavoured estimation question.

03
Final round

Typically on-site in Amsterdam or New York. Multiple interviews including trading case studies, behavioural conversations, and sometimes a live market-making exercise.

SAMPLE PROBLEM TYPES

Representative of what Flow Traders interviewers ask. Drill these and their variants on QuantPrep.

expected_value

An ETF is trading at mid-price £100. You believe the basket is worth £100.05 based on current underlying prices. The creation/redemption fee is 5 basis points. Is there an arbitrage? (Tests whether you understand ETF pricing mechanics — net of fees, the arbitrage is zero.)

market_making

Quote me a market on the number of integers less than 1 million that are not divisible by 2, 3, or 5. (Inclusion-exclusion: (1 - 1/2 - 1/3 - 1/5 + 1/6 + 1/10 + 1/15 - 1/30) × 1M ≈ 266,667. A market around 270,000 ± 20,000 is reasonable.)

combinatorics

How many ways can you arrange 10 people in a circle such that no two specific people sit next to each other? (Complement of adjacency case — tests whether you can set up inclusion-exclusion on constrained permutations.)

HOW TO PREPARE

  • ·Drill arithmetic daily before the math test window — treat it as non-negotiable.
  • ·Build ETF literacy: understand creation/redemption, primary vs. secondary market, why ETFs rarely deviate from NAV.
  • ·Practise market-making questions with explicit adverse-selection reasoning — Flow Traders tests whether you tighten or widen markets based on inferred information.
  • ·Know the core probability patterns (expected value, dice, coin, Markov chains, order statistics) with enough depth to vary the framing on follow-ups.
  • ·Be prepared to explain 'why trading' clearly — Flow Traders values candidates who visibly want the job over generalist quants shopping across firms.

COMMON MISTAKES

  • ×Skipping ETF background reading. Finalists who can't discuss ETF mechanics at a basic level signal under-preparation.
  • ×Quoting symmetric markets reflexively. Flow Traders probes adverse selection; you should widen when you suspect the counterparty has information.
  • ×Treating the math test as secondary. It's often the single biggest filter in the early funnel.
  • ×Being vague on estimation questions. Fermi-style problems require explicit assumptions; 'I don't know' without a plan fails.

FAQ

What math does Flow Traders expect?

Solid probability (expected value, conditional, Markov), mental arithmetic, and basic statistics. Less emphasis on advanced stochastic calculus than firms like Citadel.

How long does the Flow Traders interview process take?

Typically 3–5 rounds including a mental math screen, technical interviews, and a final on-site or virtual panel. Process duration varies by candidate and role.

Is QuantPrep sufficient prep for Flow Traders?

For the probability and brainteaser components, yes — QuantPrep is designed for exactly this. Supplement with arithmetic drill sites and background reading on ETF market-making.

Where does Flow Traders hire?

Primarily Amsterdam (HQ) and New York. Smaller presence in Singapore and Hong Kong. Role availability varies by cohort.

What's the difference between Flow Traders and Optiver?

Both are Dutch-origin market makers with arithmetic-heavy screens. Flow Traders specialises more on ETFs; Optiver on options. Culture and style are broadly similar but not identical — Optiver is slightly more competitive, Flow Traders slightly more process-driven.

Does Flow Traders require a finance background?

No. STEM backgrounds are the norm; quant literacy and arithmetic fluency matter more than prior finance exposure. ETF-specific context is learned on the job.

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