Senior Principal Engineer

Permanent, full-time, hybrid

Connecting clients to markets – and talent to opportunity

With 5,400+ employees and over 80,000 institutional, commercial, and payments clients, we operate from more than 80 offices spread across six continents. As a Fortune 100, Nasdaq-listed provider, we connect clients to the global markets – focusing on innovation, human connection, and providing world-class products and services to all types of investors. 

Whether you want to forge a career connecting our retail clients to potential trading opportunities, or ingrain yourself in the world of institutional investing, StoneX Group is made up of four business segments that offer endless potential for progression and growth.

Business Segment Overview: Engage in a deep variety of business-critical activities that keep our company running efficiently. From strategic marketing and financial management to human resources and operational oversight, you’ll have the opportunity to optimize processes and implement game-changing policies.

Position Purpose:

This is an opportunity to lead the modernization of a mission-critical OTC commodity options platform with direct impact on trading, valuation, risk, trade lifecycle management, portfolio analysis, and reporting across complex exotic options.

Option Prime is a stable, valuable, and deeply embedded platform used every day by the business. The opportunity is to preserve the critical business logic, pricing and risk behavior, operational workflows, and controls that make the platform valuable while moving it toward a cleaner, more scalable, and more maintainable architecture.

This is a dual-mandate role. First, you will ensure the existing platform continues to support daily trading operations reliably and without disruption. Second, you will lead the design and build of a next-generation replacement platform that reduces operational risk, improves supportability, strengthens controls, and gives the business a foundation for the next decade.

The current platform is built on aging C# / SQL Server / T-SQL architecture, with business logic distributed across application code, database logic, reports, integrations, and operational workflows. The successful candidate will bring strong engineering judgment, database architecture expertise, production ownership, and practical modernization experience to understand the existing system, validate critical behavior, and deliver an incremental migration path.

This is primarily a software engineering and platform ownership role, not a quantitative research role. You will partner closely with traders, quants, operations, and engineers, but the core mandate is technical leadership, architecture, production support, database design, migration execution, and delivery of a robust replacement system.

Why This Role Is Compelling

This role offers the chance to own a high-impact modernization from discovery through production cutover. You will work on a platform that is commercially important, operationally critical, and technically complex.

The work combines legacy-system archaeology, modern platform design, data architecture, production reliability, and trading-systems integration. It is well suited for a hands-on principal engineer who wants a role with real business impact, high technical depth, and visible ownership of a platform transformation.

You will have the opportunity to:

• Lead the modernization of a business-critical derivatives platform.
• Preserve valuable trading, valuation, risk, and lifecycle behavior while reducing legacy complexity.
• Work directly with traders, quants, operations, and engineering partners.
• Build the testing, reconciliation, observability, and migration foundations needed for safe platform replacement.
• Apply modern engineering practices, including AI-assisted workflows where appropriate, to a real-world production modernization challenge.
• Help define a platform that can support the OTC options business for the next decade.

Why This Role Matters

This is a rare opportunity to lead the modernization of a business-critical derivatives platform with direct executive visibility and real commercial impact.

The successful candidate will help define the next generation of our options trading technology: a cleaner architecture, stronger controls, lower operational risk and support burden, better scalability, and a platform that can support the business for the next decade.

For the right engineer, this is a career-defining modernization role: complex enough to require deep technical judgment, important enough to matter commercially, and broad enough to span architecture, data, reliability, migration strategy, and production delivery.

Primary Duties will include:

Own and stabilize the existing platform

• Take technical ownership of Option Prime, from legacy-system discovery through incremental production migration.
• Own day-to-day technical support and production stability during the modernization period.
• Ensure uninterrupted support for a highly active OTC commodity options business.
• Lead incident response, root-cause analysis, release management, operational controls, and change safety for a live trading platform.

Understand and preserve critical business behavior

• Reverse-engineer and document critical workflows, data models, pricing and risk behavior, trade lifecycle events, reports, reconciliations, integrations, and edge cases.
• Identify where business logic lives across application code, SQL, reports, spreadsheets, and manual workflows.
• Develop a clear understanding of which behaviors must be preserved, improved, wrapped, refactored, or retired.

Design and build the replacement platform

• Design and build the target platform architecture, including services, APIs, data pipelines, calculation workflows, reporting, auditability, observability, operational tooling, and deployment safety.
• Own the data architecture for the replacement platform, including schema design, data lineage, auditability, historical data preservation, migration strategy, reconciliation, performance, and integration with downstream systems.
• Partner with trading systems engineers, traders, quants, and operations to ensure the new platform integrates cleanly with high-performance options trading, market-data, risk, and portfolio systems.

Build safe migration and validation frameworks

• Build parallel-run and reconciliation frameworks that compare legacy and new-system outputs across trades, portfolios, market scenarios, lifecycle events, reports, and edge cases.
• Define the modernization roadmap, sequencing, cutover strategy, risk controls, and incremental delivery milestones.
• Lead technical standards around testability, observability, data quality, reconciliation, deployment safety, auditability, and production support.

Use AI-assisted engineering where it adds value

• Use AI-assisted engineering tools and workflows where appropriate to accelerate legacy-code comprehension, dependency mapping, SQL and stored-procedure analysis, test generation, documentation, refactoring, migration planning, and behavioral validation.
• Apply strong human judgment, engineering review, testing discipline, and production controls to ensure AI-assisted work meets the standards required for a live trading platform.

What Success Looks Like

In the first phase, you will understand and stabilize Option Prime, document critical workflows, reduce operational risk, and establish reliable test and reconciliation coverage around the existing platform.

Over time, you will design and deliver a modern replacement architecture, migrate functionality incrementally, validate behavior against the legacy system, and integrate the new platform with broader options trading, risk, market-data, and portfolio systems.

Long term, you will help retire a critical legacy platform while preserving the business logic, controls, and reliability that the OTC options business depends on. You will leave behind a platform that is easier to operate, easier to extend, better controlled, and better positioned to support the business for the next decade.

To land this role you will need:

Required Qualifications

• 10+ years of software engineering experience, with ownership of complex production systems.
• Demonstrated ownership of a business-critical production system where correctness, reliability, and operational continuity were mandatory.
• Strong backend and platform engineering skills in C#, Java, Python, or similar languages, with the ability to work across legacy and modern stacks. Experience with C#/.NET and SQL Server is especially valuable.
• Deep experience designing and operating data-intensive systems, including relational schema design, stored procedure analysis, query optimization, transaction boundaries, data lineage, historical data preservation, audit trails, migration, and data-quality controls.
• Strong architecture judgment around service boundaries, APIs, data flows, reliability, observability, auditability, and operational supportability.
• Experience decomposing legacy monoliths or tightly coupled legacy platforms into modern services, APIs, workflows, and data architectures.
• Strong judgment about when to preserve, wrap, refactor, or rewrite legacy functionality.
• Ability to work with messy real-world systems where business logic may live in code, SQL, reports, spreadsheets, and manual workflows.
• Experience designing validation, reconciliation, or regression-testing frameworks for complex business logic.
• Practical experience using AI-assisted engineering tools, or strong curiosity and sound judgment about how to apply them safely in real software delivery.
• Ability to communicate clearly with traders, quants, operations, and engineers.

Strongly Preferred

• Experience modernizing or migrating large legacy systems while preserving business-critical behavior and minimizing disruption.
• Experience with trading systems, derivatives, OTC options, commodity options, structured products, valuation, risk, P&L, market data, or trade lifecycle systems.
• Experience migrating from SQL Server / T-SQL-heavy architectures to modern data and service architectures.
• Experience integrating OTC, risk, or valuation platforms with listed-options, exchange-traded derivatives, market-data, or high-performance trading systems.
• Experience integrating market data, pricing libraries, trade capture, reporting, reconciliation, and downstream risk/accounting systems.
• Experience building tools for codebase analysis, dependency mapping, behavior validation, data reconciliation, production-parallel comparison, or controlled cutover.
• Experience building AI-assisted engineering workflows for codebase analysis, automated testing, documentation, refactoring, or migration.
• Experience working in high-value trading environments where correctness, auditability, and operational reliability are essential.

Who You Are

You are a hands-on principal engineer who is comfortable owning a critical legacy system while designing its replacement. You are pragmatic, production-minded, and able to work with imperfect documentation, complex databases, embedded business logic, and high-stakes users.

You know how to use modern tools, including AI-assisted engineering workflows where appropriate, to move faster. You also know where human judgment, testing, controls, and careful rollout matter most.

You do not need to be the quant who invents the pricing models, but you should be comfortable working in a derivatives trading environment where correctness and reliability are non-negotiable.

This role is best suited for someone who enjoys both legacy-system archaeology and modern platform design. It may be less suited for someone looking only for greenfield development, pure quantitative research, or management without hands-on technical ownership.

Education:

• BS/MS degree in Computer Science, Engineering or in aa related subject.

Working Environment:

• Hybrid (4 days in office per week)

Hiring Salary Range $225,000.00 - $275,000.00 per year to be determined by the education, experience, knowledge, skills and abilities of the applicant, internal equity and alignment with market data). Subject to business performance and recommendations of management, this role may be eligible to participate in an incentive compensation plan. This compensation package, in addition to a full range of medical, financial, and/or other benefits, dependent on the position, is offered.

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