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