Senior .NET Engineer
CV-LibraryNationwidepermanentPosted: 8 September 2026
Apply NowAvanti 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
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