Senior .NET / Full Stack Developer – Hybrid – £600/day Outside IR35 | C# | Azure | Event-Driven Systems | Payments | API-Driven

We have a unique opportunity for a Senior .NET / Full Stack Developer to join a payments company.

As a Senior .NET / Full Stack Developer, you’ll play a key role in building and scaling a high-throughput payments platform as the business enters its next phase of growth. This includes launching new products, enabling new partner integrations, and expanding a platform that already powers multiple live financial services products used globally.

You’ll be building on top of a modern, cloud-native platform built with .NET and Azure, designed around API-first architecture and event-driven microservices. The platform supports complex payment flows, partner integrations, and high-volume transaction processing.

This is a hands-on senior engineering role where you’ll contribute to architectural discussions, drive engineering best practices, and collaborate closely with other experienced engineers to deliver high-quality systems.

Working closely with Product, Data, Risk, and Platform teams, you’ll help evolve the platform architecture and deliver secure, scalable, and resilient distributed systems within a regulated fintech environment.

📍 2–3 days per week in the office – City of London

💰 Up to £600/day Outside IR35

🗓️ Initial 6-month contract

Responsibilities

• Design and develop high-performance .NET services powering a global payments platform
• Build and scale event-driven microservices running in Azure
• Contribute to engineering best practices across architecture, coding standards, observability, and reliability
• Work closely with product teams to design API-driven payment and partner integrations
• Collaborate with other engineers to deliver high-quality, maintainable systems
• Help evolve a scalable distributed architecture capable of handling high transaction volumes
• Contribute to improving engineering velocity, delivery quality, and platform resilience

What we’re looking for

• Strong experience building production systems with .NET / C#
• Experience building cloud-native systems in Azure
• Experience with event-driven architectures (e.g., Kafka, Service Bus, Event Grid, messaging systems)
• Proven experience building distributed systems and scalable APIs
• Experience working on payments platforms, fintech systems, or high-throughput transactional platforms
• Strong understanding of system design, reliability, and performance at scale

Senior .NET / Full Stack Developer – Hybrid – £600/day Outside IR35 | C# | Azure | Event-Driven Systems | Payments | API-Driven