Senior C# Developer within FX Options – Investment Banking – Greenfield Project
Location: Central London (3 days per week onsite)
Contract Type: Outside IR35
Salary / Rate: Up to ~£825 / day DOE
A leading investment banking team is embarking on a greenfield build of a high-performance pre-trade application and is seeking a Senior C# Developer with strong experience in Options (ideally FX Options) to join them at inception of the project.
This is a rare opportunity to influence best practices from the ground up, working directly with the FX Options trading desk to design and build a system that handles large volumes of market data in near real-time.
Key Responsibilities:
* Design and develop scalable, high-performance systems using modern C# .Net (version 9)
* Build and integrate APIs and microservices to support trading workflows
* Collaborate closely with FX Options traders to understand business requirements and deliver tailored solutions
* Contribute to architectural decisions and establish development standards for a greenfield application
* Participate in the migration of legacy monolithic systems to microservices
* (Optional) Support front-end development using ReactJS across related applications
Required Experience:
* Expert-level proficiency in C# with a strong grasp of recent language features and .NET ecosystem
* Proven experience working with FX Options trading systems or directly with Options traders
* Solid understanding of systems integration, API design, and microservices architecture
* Experience handling large-scale market data in low-latency or real-time environments
* Hands-on experience converting monolithic applications into microservices
Desirable:
* Exposure to ReactJS or willingness to contribute to front-end development when needed
This role offers the chance to work on a high-impact, greenfield build in a fast-paced trading environment, with direct access to the business and the autonomy to shape technical direction.