Senior.NET Developer in London

Are you ready to shape the future of healthcare technology by developing secure, scalable, and high-performance backend systems? Do you thrive on building modern APIs, driving integration excellence, and delivering robust solutions within complex, regulated environments? At Harris Health Alliance, part of the Harris Computer Group, we build mission-critical software that supports healthcare organisations worldwide. Innovation, reliability, and engineering quality define our approach to improving patient outcomes through technology.

As a Senior .NET Developer, you will play a pivotal role in designing, developing, and maintaining secure and scalable Web API backends, as well as integration solutions built on the latest .NET technologies. Your work will focus on delivering reliable healthcare integrations, implementing industry best practices for API security, and ensuring high performance across distributed systems. In addition to hands-on development, you will contribute to architectural decision-making, lead technical design initiatives, and mentor team members to uphold engineering excellence and deliver high-quality software solutions.

This permanent role offers full remote flexibility, with the option to work from our collaborative offices in Chippenham, Swindon, Chester, or Plymouth. Join a forward-thinking, inclusive, and innovative engineering team that values technical excellence, collaboration, and real-world impact.

What you will do

• Design, develop, and maintain high-performance Web API backend systems using the latest .NET (8+) and C#, with occasional frontend development.
• Participate in the full software development lifecycle, from requirements gathering and design through to deployment and maintenance.
• Develop and consume RESTful APIs that adhere to OpenAPI specifications and integrate with third-party services as required.
• Collaborate with cross-functional teams (QA, Platforms, Product) to ensure seamless delivery.
• Conduct code reviews, provide mentorship, and enforce best practices in software development.
• Optimise performance and scalability of existing systems.
• Ensure adherence to security, compliance, and coding standards.
• Troubleshoot, debug, and resolve complex technical issues in production and development environments.
• Contribute to architectural decisions and help shape technical direction.

What we are looking for

• 5+ years of commercial experience in software development, with at least 4 years of hands-on C# /.NET experience in production environments.
• Proven experience with Web API development, while experience with desktop application development would be an advantage (ASP.NET, Entity Framework, Web API, WinForms, WPF).
• Solid experience with PostgreSQL and/or SQL Server, including a strong understanding of database design principles.
• Demonstrated ability to produce and maintain high-quality technical documentation.
• Experience designing and implementing high-availability architectures.
• Hands-on experience with cloud platforms (preferably Microsoft Azure or equivalent).
• Familiarity with CI/CD pipelines (TeamCity, Azure DevOps, or GitHub Actions), automated testing, and infrastructure-as-code concepts.
• Proficiency with containerisation and orchestration, including Docker and Kubernetes deployments (Helm, Terraform).
• Exposure to security best practices within regulated environments, including OWASP fundamentals, authentication and authorisation standards (OAuth2, OpenID Connect), secrets management, TLS/mTLS, and certificates.
• Proven ability to lead solution designs and guide engineering efforts across multiple integrations concurrently.
• Demonstrated experience working within Agile / Scrum development environments.
• Experience mentoring junior developers or leading small teams is considered an asset.

About Us

Formed in 2024, Harris Health Alliance, a subsidiary of Harris Computer comprises four distinct brands all operating within the Healthcare sector providing software to clients worldwide. Harris Health Alliance is part of Harris Computer group, a provider of mission critical software solutions for the Public Sector, Healthcare, Utilities and Private Sector verticals throughout North America, Europe, Asia, and Australia. Harris’ strategy focuses on acquiring software businesses, strengthening and managing them well, and growing them for the future. Our companies provide mission-critical software solutions to a global customer base across various vertical markets. We are a part of Constellation Software Inc. (TSX: CSU), one of the world’s most active acquirers of software businesses. At Harris, we strive to create a respectful and united environment where all members of our globally diverse community are empowered and have equitable opportunities to succeed.

Benefits

Harris offer an extremely competitive UK employee benefits programme. 5 Personal Days leave entitlement are granted over and above the standard 25 days holiday and bank holidays. Harris also offers all UK employees an annual Lifestyle Reward amounting £325 per annum/pro rata.

Supporting your application

Our recruitment process will comprise of interviews and, at times, a written exercise, an assessment day and/or a presentation. As an equal opportunities’ employer, we want to make sure we do all we can to make this a positive experience for you. If your application is progressed, please make us aware of any adjustments or additional support we can provide you with.