Radix Trading hires Quant Technologist and Quant Researcher. Candidates report 5 interview stages. Below: what each round tests and how to prepare, the timeline, roles and a 4-week prep plan, drawn from candidate reports and Radix Trading's own recruiting pages.
Radix Trading interview: quick answer
- Stages5
- Online assessment60-90 min - coding
- Final roundOnsite: Final rounds - the toughest reported problems
- RolesQuant Technologist, Quant Researcher
Preparing for Radix Trading? Work the rounds in order in the free Radix Trading interview funnel.
The Radix Trading interview process at a glance
| # | Round | Format and length | Prep |
|---|---|---|---|
| 1 | Recruiter Screen | Phone - background + fit | Practice |
| 2 | C++ & Algorithms | 60-90 min - coding | OA guidePractice |
| 3 | Probability & Numerical | 45-60 min - video | GuidePractice |
| 4 | Linear Algebra & Optimization | 45-60 min - research | GuidePractice |
| 5 | Onsite Hardest Rounds | Final rounds - the toughest reported problems | Practice |
Stages are listed in the order candidates report them. Formats come from candidate reports and change between cycles, offices and teams; not every candidate sees every stage.
Every Radix Trading round: what it tests and how to prepare
1Recruiter Screen
An intro conversation about background and interest, sometimes with a quick technical warm-up.
How to prepare
- Know why this firm / why the role.
- Warm up mental math + basics.
- Think aloud.
2C++ & Algorithms
C++ implementation and numerical problems: reference-counted shared_ptr, fixed-buffer allocator, stable summation (Kahan), tournament min-comparisons.
Question types: mostly coding, especially data structures, greedy, C++ and two pointers and sliding windows. Latest candidate report for this round: Jul 2026.
How to prepare
- C++ internals -- smart pointers, allocators, memory.
- Numerical stability -- Kahan/pairwise summation, cancellation.
- Prove complexity (e.g. n + ceil(log2 n) - 2 for max+2nd).
Radix Trading online assessment guide →Practice this round (12 questions) →
3Probability & Numerical
Probability, combinatorics, and statistics with a numerical bent (variance computation, sampling).
Question types: mostly probability, combinatorics and statistics, especially numerical methods, symmetry, uniform distribution and binomial distribution. Latest candidate report for this round: Jun 2026.
How to prepare
- Variance computation -- avoid catastrophic cancellation.
- Sampling -- uniform paths, returning walks.
- Clean combinatorial counting.
Full Probability & Numerical guide →Practice this round (15 questions) →
4Linear Algebra & Optimization
Linear algebra (eigenvalues, conditioning), optimization (LP/least-absolute-deviations), regression, and stochastic processes.
Question types: mostly linear algebra, optimization and regression, especially matrix operations, complexity analysis, eigenvalues and expected value. Latest candidate report for this round: Jul 2026.
How to prepare
- Eigenvalues/conditioning of structured matrices.
- LP / L1 minimization formulations.
- OLS + Gauss-Markov properties.
Full Linear Algebra & Optimization guide →Practice this round (9 questions) →
5Onsite: Hardest Rounds
The hardest reported Radix Trading problems across every topic.
Question types: mostly coding, linear algebra and optimization, especially data structures, complexity analysis, dynamic programming and sorting and searching. Latest candidate report for this round: Jun 2022.
How to prepare
- Expect the hardest variants across all topics.
- Stay composed under follow-ups.
- Connect the math back to the desk.
Practice the Radix Trading rounds in order
Each round in the Radix Trading funnel has its own practice set, with worked solutions and progress tracking. A free account saves your progress across rounds.
A 4-week Radix Trading prep plan
Built from the order of Radix Trading's rounds and the topics in each round's practice set. Compress it if your first interview is sooner.
| When | Focus | What to do |
|---|---|---|
| Week 1 | Foundations | Review coding, probability and linear algebra, the topics that dominate Radix Trading's practice sets. Start with Quant coding course and Probability course. Work the easy and medium questions in the Radix Trading question set. |
| Week 2 | Early rounds: Recruiter Screen, C++ & Algorithms, Probability & Numerical and Linear Algebra & Optimization | Practice coding, probability and combinatorics under time pressure, and read the OA guide. Add a daily mental-math drill. Talk every answer through out loud; interviewers score the reasoning. |
| Week 3 | Later rounds: Onsite | Move to linear algebra, optimization and statistics. Read how quant superdays work. |
| Week 4 | Rehearse the full loop | Run each practice round in order, redo the questions you missed, and prepare two project stories plus a specific answer to "why Radix Trading?" (see behavioral questions at trading firms). |
About Radix Trading
| Firm type | Proprietary high-frequency trading firm |
|---|---|
| Trading style | C++ + numerical + research · Ultra-low-latency / HFT |
| Founded | 2012 |
| Headquarters | Chicago, IL (+ NYC) |
| Other offices | false |
| Capital | Proprietary (private) |
| Employees | ~150+ |
| Reported performance | ~$300-450M/yr (est.) |
| Technical focus | Deep C++ implementation and numerical problems |
Culture
Heavy on numerical methods and clean systems code.
What the interviews feel like
Hard C++/algorithms and numerical-analysis problems (catastrophic cancellation, stable summation, allocators), plus probability and linear algebra.
Practice for Radix Trading on QuantVault
Practice
Courses
Games and drills
Further reading
- How quant superdays work
- Behavioral questions at trading firms
- Mental math for trading interviews
- C++ and low-latency interview questions
- Market-making game interview guide
- The quant interview process, explained
Similar firms to compare
Firms with a similar business and interview style. Many candidates interview at several of them in the same cycle.
Sources and how this guide is built
- Updated October 20, 2026; firm data last reviewed May 30, 2026.
- Round detail draws on 20 questions candidates report from Radix Trading interviews (the most recent report across all rounds is from Jul 2026). A separate curated Radix Trading question set of 49 problems collects the most useful practice for this firm.
- Radix Trading's own pages: Radix Trading.
- Public candidate reports and outside interview guides are cross-checked against each other. Where they disagree the page says "reports differ"; details from a single source are marked as candidate reports.
- No actual interview questions are reproduced on this page. The questions, with worked solutions, are in the practice rounds.
Radix Trading interview FAQ
How many rounds are in the Radix Trading interview?
Candidates report 5 stages: Recruiter Screen, C++ & Algorithms, Probability & Numerical, Linear Algebra & Optimization, Onsite. The exact number varies by cycle and team.
Is there an online assessment at Radix Trading?
Candidates report one: 60-90 min - coding. C++ implementation and numerical problems: reference-counted shared_ptr, fixed-buffer allocator, stable summation (Kahan), tournament min-comparisons.
What happens in the Radix Trading final round?
Onsite (Final rounds - the toughest reported problems). The hardest reported Radix Trading problems across every topic.
How should I prepare for the Radix Trading interview?
Prepare round by round over about four weeks: foundations first, then the early rounds (Recruiter Screen, C++ & Algorithms, Probability & Numerical), then the later rounds, then a full rehearsal. Each round has its own practice set on QuantVault, and the online assessment has a dedicated guide.
What does Radix Trading do?
Radix Trading is a proprietary high-frequency trading firm headquartered in Chicago, IL (+ NYC).
Start preparing for Radix Trading
Open the interactive Radix Trading interview funnel: every stage with its practice set, from the first screen to the final round. Create a free account to save your progress.