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HRT

Hudson River Trading
Interview Guide

Known for its engineering-first culture and "The Labs". HRT is one of the most prestigious HFT firms in the world, responsible for over 5% of all US equities trading.

See QuestionsThe Process
2002
Founded
NYC
Headquarters
900+
Employees
$400k+
New Grad TC

The Interview Loop

HRT has a very standardized and efficient process.

1

Online Assessment (CodeSignal)

Unlike other firms, HRT takes the OA very seriously. You must score near perfect (830+ on CodeSignal) to move forward. Expect 4 questions in 60-70 minutes. Usually 2 easies, 1 medium, and 1 hard implementation problem.

2

Phone Screen (C++ / Systems)

A 45-minute technical screen with an engineer. For standard SWE roles, this will be pure C++ trivia and coding. For Algo roles, expect probability or math puzzles.
Common topic: "Implement a shared_ptr from scratch".

3

The Onsite (3-5 Rounds)

Used to be in their NYC office in 4 World Trade Center, now often virtual.

  • Systems Round: OS internals, networking, kernel bypass.
  • Coding Round: Complex algorithms (Graph/DP/Trees).
  • Debugging Round: Find the bug in this giant C++ codebase.

Real Interview Questions

What candidates have reported recently.

C++ / Systems

The "Matching Engine"

Design a limit order book matching engine. How do you handle buy/sell orders? What data structure gives O(1) matching and O(1) cancellation?

View Hint
Use a HashMap of Price → LinkedList of Orders. Maintain a max-heap for Buy prices and min-heap for Sell prices? No, heaps are O(log N). Use a direct array or red-black tree if range is large.
Probability

Expected Value of Max

Pick 3 random numbers between 0 and 1. What is the expected value of the largest number? Generalize to N numbers.

View Hint
For N variables, E[Max] = N / (N + 1). So for 3, it's 3/4.
Low Level

Volatile vs Atomic

What is the difference between `volatile` and `std::atomic` in C++? Can `volatile` be used for thread synchronization?

View Hint
Volatile prevents compiler optimization but guarantees nothing about thread safety or memory ordering. Atomic guarantees atomicity and memory visibility across threads.
Algorithms

Sliding Window Max

Given an array and a window size k, find the maximum element in each window. Must be linear time O(n).

View Hint
Use a Monotonic Deque (Double Ended Queue). Store indices. Remove smaller elements from back when adding new one.

Life at "The Labs"

HRT often calls itself "The Labs" because it feels more like a top-tier computer science research lab than a stuffy finance firm. If you are an engineer at heart, this is arguably the best place to be. The feedback loop is incredibly short—you can write code in the morning and have it trading live in the afternoon.

The culture is notably "nice" compared to the cutthroat reputation of some competitors. Free breakfast, lunch, and dinner, plus an incredible office view of the Statue of Liberty (if you're in NYC).