Software Engineer

Senior .NET Developer - Hybrid - Up to £700/day Outside IR35 | C# | Azure | Event Driven Systems | Kafka | CosmosDB

We have a unique opportunity for a Lead .NET Developer to join a payments company.

As the Senior .NET/Full Stack Developer, you’ll play a key role in shaping 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 technical role where you’ll help drive engineering best practices, contribute to architectural decisions, and mentor developers while remaining close to the code.

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

2 -3 days per week in the office - City of London

Up to £700/day Outside IR35

Responsibilities

• Lead the design and development of high-performance .NET services powering a global payments platform
• Build and scale event-driven microservices running in Azure
• Drive best practices across architecture, coding standards, observability, and reliability
• Work closely with product teams to design API-driven payment and partner integrations
• Mentor and support engineers across the team while contributing hands-on to critical 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)
• Experience with Azure Cosmos DB
• 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
• Ability to lead technically while remaining hands-on in development