Senior Fullstack .NET Developer

Avanti Recruitment; Ribble Valley; On-site; GBP 63,000 - 77,000; Full time

Benefits offered by this job

Pension

Holiday allowance

Employee benefits

Job summary

Avanti is seeking a Senior Fullstack .NET Developer with strong React experience to join a software business modernising a core platform. This hands-on role focuses on building scalable services, APIs and frontend features while guiding architecture decisions.

You will work in a test-driven environment, increase automated test coverage, and contribute to the overall quality of the codebase. The role is remote-first with occasional in-person collaboration near West London and the M4 corridor,

Qualifications

• Strong C#/.NET experience in large-scale applications.
• Proficiency with React frontend development.
• Experience with TDD and automated testing.
• Ability to design and contribute to software architecture decisions.
• Ability to work independently and own technical problems.

Responsibilities

• 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.

Skills

C#/.NET

React

TDD

REST APIs

CI/CD

Architecture

Tools

SQL Server

WinForms

CI/CD tooling

Job description

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.