Senior Developer

Stealth B2B SaaS Startup; Greater London; On-site; GBP 90,000 - 130,000; Full time

Job summary

Stealth B2B SaaS Startup is seeking a Senior Developer to join SAL and help shape the future of our products. You will work with our Head of Development to design and build the next generation of our platform while enhancing the Windows desktop application and web-based financial tools.

You will influence architecture, technical direction, and engineering standards in a small, collaborative team that values practical, value-driven work and open discussion.

Qualifications

• Hands-on experience with WPF and MVVM architectures.
• Proficient in SQL Server and Entity Framework Core.
• Knowledge of authentication/authorization: OpenID Connect, OAuth 2.0, RBAC.
• Strong multithreading and concurrent programming skills.
• Experience with unit and integration testing.
• Experience with Azure or similar cloud platforms.
• Secure coding practices and cybersecurity awareness.

Responsibilities

• Maintain and enhance existing software platforms.
• Collaborate with Head of Development on next-generation products.
• Contribute to architectural discussions and technical decisions.
• Research, evaluate, and introduce new technologies.
• Produce and maintain technical documentation.
• Share knowledge and support team members.
• Continuously improve products, processes, and engineering practices.

Skills

WPF & MVVM

SQL Server

EF Core

OpenID Connect

OAuth 2.0

RBAC

Multithreading

Unit testing

System design

Azure

Security

Cybersecurity

Job description

We're looking for a Senior Developer to join SAL and help shape the future of our

products.

You'll work closely with our Head of Development to design and build the next

generation of our platform while continuing to enhance and support our existing

software, including our Windows desktop application and web-based financial

We're currently modernising our software solutions, so your ideas, experience, and

technical expertise will have a real impact. You'll play an important role not only in

development, but also in influencing architecture, technical direction, and engineering

standards.

We're a small team, which means everyone has a voice. Communication is just as

important as technical ability. Writing great code is only part of the role, you'll also need

to collaborate effectively, explain technical decisions clearly, and work closely with

colleagues across the business.

We work in an agile environment, but we're pragmatic rather than process-driven. We

care about delivering value, solving real problems, and continuously improving how we

work.

Responsibilities

• Maintain and enhance our existing software platforms.
• Work closely with the Head of Development to design and build our next-generation products.
• Contribute to architectural discussions and technical decision-making.
• Research, evaluate, and introduce new technologies where appropriate.
• Produce and maintain technical documentation.
• Share knowledge and support other members of the team.
• Continuously look for ways to improve our products, processes, and engineering practices.

Who You Are

We're looking for someone who is not only technically strong but also enjoys working

with people.

You are:

• A clear and open communicator who enjoys collaborating and keeping others informed.
• Empathetic and customer-focused, always considering how your work improves the experience for the people using our products.
• Thoughtful and considerate of your teammates, leaving code and systems in a better state than you found them.
• Someone who naturally supports others and is happy to share knowledge.
• Comfortable making mistakes and viewing them as opportunities to learn and improve.
• Curious and willing to challenge existing approaches respectfully when you believe there's a better solution.
• Detail-oriented, understanding that the small things often make the biggest difference.
• Passionate about learning and continuously developing your skills.
• You recognise that AI has fundamentally changed the software development landscape, and you embrace the opportunity to use AI responsibly to help us build better software, faster, without compromising quality or maintainability.

Technical Requirements

• WPF and MVVM
• SQL Server and Entity Framework Core
• OpenID Connect, OAuth 2.0 and Role-Based Access Control (RBAC)
• Multithreading and concurrent programming
• Unit and integration testing
• System design and software architecture
• Experience with Azure or similar cloud platforms
• Experience building secure applications
• A good understanding of cybersecurity principles

Nice to Have

• An appreciation for user experience (UX) and usability
• Experience using AI-assisted development tools such as Codex and Claude
• Experience designing AI-powered development workflows and effective prompt

How We Work

We're a small, experienced engineering team where everyone has the opportunity to

make a meaningful contribution.

We value collaboration over ego, practical solutions over unnecessary complexity, and ideas, and believe the best solutions come from open discussion rather than hierarchy.

If you're someone who enjoys taking ownership, working closely with others, and

building software that genuinely makes a difference, we'd love to hear from you.