Hudson River Trading Interview Guide

After your resume passes screening, the first hurdle is usually a timed coding test, most often delivered through HackerRank. Candidates commonly report three problems at LeetCode Medium to Hard difficulty, to be solved in a language of your choice (C++ and Python are the most common).

The flavour is not generic algorithm trivia. HRT tends toward problems that mix coding with quantitative reasoning: implementing a simulation, processing a stream of timestamped trades to calculate profits, or coding up something numerical under time pressure. One frequently reported task is to filter through sets of trades with timestamps and calculate profits, which rewards clean data handling more than clever tricks.

To prepare, drill LeetCode Medium/Hard problems and Project Euler, but bias toward problems that involve simulation, combinatorics, and data processing. Make sure you can write correct, readable code quickly in your strongest language. Speed and correctness both matter here.

Candidates who clear the OA move to one or two technical phone or video screens. These typically split into two themes:

1. Math and Probability: Expect expected value questions, conditional probability, and brainteasers. Several candidates note that the problems are variations on classics from the green book (A Practical Guide to Quantitative Finance Interviews by Xinfeng Zhou), so working through that material is high-yield. A representative HRT problem: Romeo and Juliet each arrive at a random time between 0 and 1 hour, uniformly and independently. The first to arrive waits 15 minutes, then leaves. What is the probability they meet? (The clean way to solve it is geometrically, on the unit square, finding the area where the absolute difference in arrival times is at most 0.25.)
2. Coding: A live coding round where you write and explain code in real time. Interviewers care as much about how you reason out loud as about the final answer, so narrate your logic clearly while you type. A reported example: live code a poker simulation to find the best hand within 45 minutes.

HRT interviewers move fast and push you to think on your feet, so train your reaction speed and get comfortable talking through your approach while coding.

To prepare for the probability side, work through our brainteaser database and focus on probability and expected value questions. For the EV-under-pressure mindset, our market making games are strong practice.

The final stage is a sequence of 1-on-1 interviews, often around five rounds, with quants and algo developers. These cover a mix of:

• Coding interviews: Deeper than the phone screen, sometimes touching on C++ and systems-level thinking, especially for Algo Developer roles where low-latency performance matters.
• Probability and brainteaser rounds: More expected value, Markov processes, and statistics, applied under pressure.
• EV / strategy games: A common format is to develop an optimal strategy in a dice or card game, then write code to validate it through simulation. This tests whether you can move fluidly between a mathematical argument and a working implementation.
• Data analysis: You may be handed a dataset and asked to analyse it in a Python Jupyter notebook. This is exploratory rather than algorithmic, testing how you reason about real data.

The recurring theme across the onsite is the loop between math and code. HRT wants people who can derive an optimal strategy and implement it, not specialists in only one half.

Core technical topics to have solid: conditional probability, Bayes' theorem, Markov chains, expected value, combinatorics, hypothesis testing, and regression, plus comfortable Python and (for some tracks) C++.

For the strategy-game rounds specifically, play our Dice and Card market making games on higher difficulty until the EV reasoning is automatic, then practice coding small simulations to confirm your answers.

Two things separate strong HRT candidates from the rest, and neither is captured by a study list.

The first is genuine fluency moving between math and code. Plenty of candidates can solve a probability problem, and plenty can write a clean simulation, but HRT specifically tests whether you can do both in the same breath: derive an optimal strategy, then implement it to check your own work. Build that as a single habit rather than two separate skills. When you practice expected value problems, write the simulation that confirms the answer, every time, until the loop feels automatic.

The second is how you behave under the pace. HRT interviewers move fast and judge your reasoning as much as your final answer, so silence reads as being stuck. Get comfortable narrating your logic out loud while you write code, and time yourself on LeetCode Medium/Hard and on brainteasers so that speed is not the thing that trips you up. The math itself is largely standard, much of it variations on green book problems, which means the differentiator is rarely whether you know the material and usually whether you can apply it quickly and explain it clearly.

One last point that is easy to neglect: be ready to say why HRT specifically. This is a technology-driven, deliberately secretive firm that builds nearly everything in-house, down to the network hardware. Generic enthusiasm for trading is not enough. Tie your answer to the engineering-first culture and the multi-asset liquidity work, because that is what the firm actually identifies with.

The HRT interview rewards candidates who are genuinely strong in both quantitative reasoning and coding, and who can move between the two without friction. It is less forgiving than a pure-trader interview for anyone whose programming is shaky, and the pace inside each round is deliberately demanding.

The most effective preparation combines three things: drilling green book style probability and expected value problems, getting fast and clean on LeetCode Medium/Hard and simulation-style coding, and practicing the specific habit of validating a strategy through code. Candidates who treat the process casually tend to underestimate exactly how high the combined bar is.

Approach it with serious, structured preparation, stay calm under the fast pace, and let your thinking show. Each round is another chance to demonstrate that you can both find the optimal answer and build it.