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Software Engineer

Simplex Trading · Chicago, IL · $125,000–$200,000 a year · Development

Posted Sep 11, 2026 · We last checked this listing on Oct 6, 2026

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Likely interview questions for this role

Written from this job description, not a generic list. Each one notes what the interviewer is really checking.

About your past

Tell me about the most performance-sensitive code you have written. How did you measure and improve it?

What they are checking: Whether they optimize based on measurement rather than guesses, which matters in high speed trading.

Tell me about a time you worked closely with non-engineers, like traders, to build something they needed.

What they are checking: Ability to translate trading needs into software and work side by side with users.

Describe a bug that took you a long time to find. What finally cracked it?

What they are checking: Persistence and a systematic approach to hard problems.

What would you do

Your main experience is in Java or C#. How would you get productive in our C++ codebase on Linux?

What they are checking: Honest self-assessment and a real plan for learning, since the posting accepts other languages.

A trading strategy is behaving oddly in production during market hours. How do you debug without making it worse?

What they are checking: Judgment under pressure, including when to stop trading and how to investigate safely.

About the work

In C++, how would you avoid memory allocation on a hot path?

What they are checking: Knowledge of object pools, preallocation and why allocation causes latency spikes.

What happens in a CPU cache when your data structures are laid out badly? How would you fix it?

What they are checking: Understanding of cache locality, which separates fast trading code from merely correct code.

How would you design an execution engine component that receives market data and sends orders with low latency?

What they are checking: Ability to reason about the full data path and where time is spent in a trading system.

What makes C++ code reusable and reliable over years, not just fast today?

What they are checking: Whether they balance speed with clean design, testing and maintainability.

What Linux tools do you use to see what a process is doing?

What they are checking: Practical Linux debugging skill with tools like perf, strace or top.

How would you analyze a large amount of market data quickly to answer a trader's question?

What they are checking: Whether they can choose the right tools and approach for high speed data analysis.

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The full job description

As published by Simplex Trading.

Our employees are our greatest asset. We have spent years building a team of talented, dedicated technologists, data-driven traders, and expert leaders with an emphasis on our core pillars: People, Process, Trading Edge, and Technology. Simplex is an in-office organization, helping to foster a collaborative and communicative culture. Career Description Simplex is looking for smart, curious, and driven individuals to join our technology team. Technology at Simplex is the core of the business. We are a technology company, specializing in high speed trading. We are looking for great people to work on all aspects of our trading system. What will you be doing? • Work on our system from trading algorithm development, to high speed data analysis, and intelligent execution engine design • Design, build, and maintain efficient, reusable, and reliable C++ code on Linux • Other opportunities as assigned Skills and Experience: • 4+ years experience working with a high level language (ex C++, Java, C#) • Some C++ experience is a plus • Linux/Unix exposure • Previous financial industry experience is a plus • Computer science or engineering degree or real world experience   Annual base salary ranges from $125,000 to $200,000, and is influenced by a number of factors, including qualifications and experience. This role is also eligible for an annual discretionary bonus, of which can be a significant portion of total compensation. This full time role is also eligible for other forms of compensation and benefits including health/dental/vision insurance, and 401(k) contributions.     Software Engineer pay range $125,000 — $200,000 USD Why us? Founded in Chicago in 2004, Simplex is a leading, technology-driven, proprietary market-making firm. We work with the most advanced technology and software in the market, and we’ve continued to remain at the forefront of the industry by always focusing on innovation, automation, and data-driven analysis. We also leverage our experience and expertise to make strategic investments and capitalize on opportunities in the venture capital markets with promising, early-stage financial and technology start-ups.  PLUS, the goods! • Benefits: Excellent a la carte Medical/Dental/Vision (free employee coverage!), 401(k) match, generous parental leave! • The Office: The kitchen is stocked with snacks, and beverages; you also have daily stipends for breakfast and lunch!  • Tuition Reimbursement: As an investment in our employees’ careers and the company’s future, we offer educational assistance to provide employees with professional development opportunities that increase their skills and enhance their contributions to the organization! • Employee Discounts: To gyms, national brands, and more! • Building:  We are located in the Federal Reserve building. As a tenant, you have access to a building gym and a full cafeteria. We are easily accessible to all public transportation. • Charity Match: We match up to $2,000 a year in donations to the charities of your choice! • Fun Events: In-person happy hours, celebrations throughout the year, game nights, video game fun, and so much more! Simplex is an Equal Opportunity Employer. Simplex and its recruitment partners may use artificial intelligence (AI) tools to support certain aspects of the recruiting and hiring process. Final hiring decisions are made by humans. For all job postings, Simplex may use AI to review and analyze applications, resumes, interviews, and applicant responses.  Simplex complies with applicable federal and state laws governing AI use. Applicants may still request reasonable accommodations. For more information related to AI or to request an accommodation, please contact  HR@simplextrading.com . 

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