Senior Full Stack C# Developer | Contract | Inside IR35 | London

Our investment banking clients is seeking a Senior Full Stack Developer to join its Front Office FX technology team, building and enhancing business-critical systems used across London, New York and Singapore.
This role sits within the FX Deal Capture team and is ideal for an experienced engineer who enjoys designing, building and supporting large-scale distributed applications. 
You'll work on systems responsible for trade capture, post-trade workflows and strategic enhancements used daily by traders and operational teams across the bank.

What You'll Be Doing

• Building new features across a modern C#/.NET platform
• Designing and developing REST APIs and backend services
• Enhancing deal capture and post-trade processing systems
• Working on messaging and event-driven architecture initiatives
• Refactoring and modernising existing applications
• Collaborating with developers, business users and technology stakeholders
• Taking ownership of deliveries across the full SDLC

Essential Skills

• Strong C# and .NET /.NET Core development experience
• Experience building REST APIs and enterprise applications
• Strong understanding of software architecture and design patterns
• TDD and automated testing experience
• Database development experience
• Experience working on large-scale, business-critical systems

Desirable Skills

• Kafka
• IBM MQ
• React
• TypeScript
• Python
• Front Office or financial markets experience
• AI-assisted development tools such as Claude Code, Copilot or similar