Senior Software Developer

Location: Cardiff (Office‑based, 5 days a week)

Salary: £55,000 – £65,000 base (DOE) + up to £3,000 annual bonus

Start Date: Immediate start available, but willing to wait for the right candidate

Are you an accomplished senior software developer with a proven track record in .NET? Join us at an exciting time in our journey, where you’ll help shape the future of our products as we modernise our enterprise applications with latest .NET technologies and event‑driven SaaS microservice architecture to deliver enterprise‑scale solutions. At Advanced Secure Technologies, we’re a fast‑growing, innovative company on a mission to protect organisations from document fraud through cutting‑edge security solutions. Based on site in St Mellons, Cardiff, we’re expanding and need another skilled senior developer to help us scale.

What You’ll Do

• Play a key role in the design and delivery of new features and platform improvements using .NET 10 and other modern technologies, contributing as a senior individual contributor within one of our collaborative engineering teams.
• Share ideas, solve complex technical problems, and help shape the future technical direction, architecture and engineering standards of our products.
• Take ownership of team sprint delivery, facilitating sprint activities, coordinating priorities, resolving blockers and helping ensure releases and wider project deliverables remain on track and delivered successfully.
• Support and mentor other developers through technical guidance, collaboration, code reviews and sharing best practice, while also supporting their career development and contributing to a collaborative, high‑performing engineering culture.

Requirements

• Proven experience operating successfully at senior developer/engineer level within commercial software teams, making strong hands‑on technical contributions as a senior individual contributor.
• 7+ years commercial experience delivering modern C# .NET solutions.
• Strong commitment to engineering best practices, including writing clean, maintainable and testable code, with experience applying unit and integration testing standards within modern development teams.
• Experience of Clean Architecture or similar modern approaches, such as hexagonal or onion architecture, beyond traditional N‑tier designs.
• Strong problem‑solving skills, attention to detail, excellent organisation and clear communication skills, with the ability to collaborate effectively across diverse engineering teams and the wider business.
• Experience mentoring, guiding and supporting other developers, helping them grow through collaboration, technical guidance and knowledge sharing.

Bonus Points For

• Working with enterprise‑scale software, microservices, event‑driven architecture or SaaS product development.
• Experience with TDD, DDD, secure coding/OWASP practices, Azure DevOps, CI/CD pipelines and cloud platforms like Azure.
• Experience with some of the tech we use: .NET Blazor, EF Core, SQL, Redis, Elasticsearch, RabbitMQ, Docker, Kubernetes or Blockchain.
• Experience using AI tools to improve developer effectiveness, team productivity and the quality or speed of software delivery.

Benefits

• Competitive salary £55,000 - £65,000 (DOE) + monthly performance bonus.
• A clear career pathway through our Senior Developer grades and beyond with mentoring and skill development support.
• 25 days holiday + Bank Holidays.
• Training and development time, plus training budgets for courses/exams.
• Free gym, secure parking, free eyecare and a fully stocked kitchen.
• Access to PerkBox significant retailer discounts.
• Free Private online GP.
• Employee Assistance Programme including specialist clinical support.
• Company car and cycle‑to‑work schemes.
• A fun, supportive culture with birthday treats and epic office events.

Interview Process

• Introductory call (45 min): A chance for us to get to know you, and for you to get to know us. We’ll cover your experience, a few competency‑based questions, and some light technical discussion.
• Technical assessment (90 min): Technical questions and discussion around your approach and problem‑solving, includes a 30‑minute practical coding exercise focused on real‑world problem solving.
• Final conversation (20 min): Meet our Managing Director for an informal chat about the role, the team, your potential impact, and the growth opportunity available to you.

Location and hours

Onsite, Eastern Business Park, St Mellons, Cardiff, Wales.

Min Hours 37.5 hrs per week, 8.30 am to 5 pm Monday to Friday, with up to one hour for lunch.

On Site Working

We’re an office‑based team because our culture thrives on collaboration and hands‑on support, especially as we grow quickly and onboard new team members. While we don’t offer fully remote or fixed hybrid work, we’re flexible when life happens – ad hoc home working is always an option.

Diversity & Inclusion

Advanced Secure Technologies is an equal opportunity employer, proud of our ongoing efforts to foster diversity and inclusion. We welcome applicants from all backgrounds and process your personal data in accordance with our Privacy Notice.