Senior Fullstack .NET Developer

Avanti is working with an established software business that is investing heavily in the modernisation of one of its core platforms and is looking for a Senior Fullstack .NET Developer with strong experience in React. This is a hands-on engineering role where you'll help evolve an established business-critical application into a more modern, scalable architecture. The focus will be on improving the underlying platform, building modern services and APIs, increasing automated test coverage and gradually moving functionality towards a modern web-based frontend. You'll remain very hands-on with C#/.NET development while also contributing to software design, architecture and technical decisions across the wider engineering team. The business places a strong emphasis on the engineering quality, automated testing and test-first development, so strong TDD experience is essential. What you'll be doing

• Building and maintaining applications and services using C# and modern .NET
• Designing and developing REST APIs
• Developing frontend functionality using React
• Helping modernise an established application architecture
• Improving automated test coverage and overall code quality
• Working in a test-first development environment
• Contributing to software design and architecture decisions
• Improving platform maintainability, scalability and long-term technical direction
• Supporting existing systems while helping build their future replacement Technology Environment:
• C# / .NET 8
• REST APIs
• React
• SQL Server
• Automated testing
• TDD
• CI/CD
• Cloud technologies There is also some exposure to established desktop WinForms technologies within the existing platform, although previous experience in this area is not essential. Essential Skills:
• Strong C#/.NET
• React
• TDD
• REST APIs
• CI/CD knowledge
• Experience contributing to architecture / design and technical decisions
• Ability to work independently and take ownership of technical problems Experience with cloud platforms, legacy application modernisation or AI-assisted development would be useful. Working arrangement The role is remote first, with some initial time spent with the team during onboarding, and occasional in person collaboration thereafter (West London / M4 corridor) – costs covered. Interview process The process will involve an initial video call which will be a technical discussion, followed by a final-stage video interview including a practical coding element following TDD. Package Salary up to £70,000, plus pension, holiday allowance and additional employee benefits. If interested in the position then click Apply Now