Staff Full Stack Engineer

We’re seeking a seasoned .NET Technical Lead with deep expertise in .NET/C# and WPF to guide the evolution of our LegalTech products. This is a hands-on leadership and technical role where you’ll set technical direction, architect scalable systems, and ensure the delivery of high-quality, performant applications—ranging from modern WPF-based desktop software to robust cloud services.

You’ll play a critical part in mentoring engineers, shaping architectural decisions, and embedding best practices, while still contributing meaningfully to the codebase.

This is a unique opportunity to lead from the front at a fast-growing company whose products are trusted by some of the world’s leading law firms and legal teams.

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Technical Leadership & Strategy

• Define and drive the technical vision, architecture, and roadmap for both desktop and backend services.

• Lead architectural design sessions, ensuring scalable, secure, and maintainable solutions.

• Champion engineering best practices, including early-stage quality planning (Shift Left), design patterns, automated testing, and CI/CD implementation.

• Evaluate and introduce emerging technologies (e.g., AI-assisted coding, cross-platform frameworks) to improve productivity and product innovation.

Application Development & Delivery

• Lead the development of complex WPF-based applications following modern design patterns such as MVVM, leveraging data binding, templating, and modular architecture.

• Oversee and contribute to the implementation of scalable backend services, APIs, and libraries using .NET Core and cloud platforms like AWS or Azure.

• Ensure high-quality and testable code through proactive practices such as early test planning, TDD, code reviews, and automation.

• Enable rapid release cycles with strong DevOps practices, ensuring confidence in every deployment.

Quality & Engineering Excellence

• Promote and apply principles such as SOLID, DRY, KISS, and Shift-Left quality to reduce defects early in the SDLC.

• Lead initiatives to embed testing into architecture and development, improving testability and enabling earlier defect detection.

• Use profiling and diagnostics tools to address performance, memory, and runtime optimizations.

• Refactor legacy systems to modern standards, boosting maintainability, coverage, and stability.

• Leverage tools like Autofac and clean architecture patterns to maintain loosely coupled and testable codebases.

Team Mentorship & Collaboration

• Act as a mentor and coach, helping engineers improve their technical depth, test-first mindset, and overall quality focus.

• Collaborate with Product Managers, Designers, and other Engineering Leads to ensure product and engineering goals remain aligned.

• Help recruit, onboard, and develop top-tier engineers, growing a high-performance team.

Innovation & Continuous Improvement

• Advocate for and implement AI-assisted development tools (e.g., GitHub Copilot, Claude Code) to boost engineering velocity and quality.

• Identify and implement opportunities to automate workflows, reduce technical debt, and drive continuous delivery excellence.

• Drive a culture of early feedback, enabling faster and more reliable development through improved observability and testing strategies.

• 8+ years of professional software development experience with .NET/C#, including 3+ years in a technical leadership role.

• Proven track record architecting and delivering Windows desktop applications using WPF, including custom controls, UI animations, and advanced XAML.

• Strong backend expertise with .NET Core, RESTful API design, and scalable service architecture.

• Familiar with Shift-Left testing approaches, embedding quality early in the SDLC and enabling team-wide accountability for code correctness.

• Deep understanding of object-oriented design, design patterns, and principles like SOLID and TDD.

• Proficient with Visual Studio and/or JetBrains Rider, and skilled in using ReSharper for code quality and refactoring.

• Familiarity with AI-assisted tools like GitHub Copilot and Claude Code.

• Skilled with relational databases (e.g., PostgreSQL) and CI/CD pipelines using modern DevOps toolchains.

• Demonstrated leadership and mentoring skills with the ability to influence architecture and cross-functional decisions.

• Pragmatic, strategic, and hands-on problem-solver who balances innovation with technical stability.

• Comfortable working in a fast-paced, agile environment.

• Experience in product-focused or startup environments with rapid iteration cycles.

• Prior experience building VSTO Word Add-Ins.

• Familiarity with cross-platform frameworks like .NET MAUI, Blazor, or Avalonia.

• Knowledge of performance profiling, optimization, and enterprise-scale desktop deployment.

• Exposure to domain-driven design, microservices, or distributed systems.

• 💰 Competitive salary & annual bonus

• 📈 Equity in Definely

• 🎉 Quarterly team socials & annual company offsite

• 🏠 Hybrid working (Tues & Thurs in-office) + 🌍 1 month “work from anywhere”

• 🏖️ 25 days holiday + bank holidays

• 📚 £750 annual learning & development budget

• 🩺 Private healthcare (incl. dental & optical)

• 👶 Enhanced parental leave

• 🚲 Additional perks: Cycle to Work, Workplace Nursery salary sacrifice scheme, and top-quality equipment

At Definely, we’re on a mission to simplify the way legal professionals access and understand complex information in legal documents. Trusted by a global community of customers, our LegalTech solutions integrate seamlessly into lawyers' daily workflows, making it easier to draft, review and navigate even the most complex contracts.

Our products provide instant access to essential information, enabling legal teams to review clauses and provisions in context, reduce risk and work more efficiently – all without disrupting their flow. At Definely, we’re dedicated to solving real challenges faced by legal professionals.

Joining Definely means becoming part of a forward-thinking, collaborative team that prioritises innovation and people. We create a supportive environment driven by a shared commitment to connection, growth and success.

Recognised in the top 25 of Deloitte's prestigious UK Technology Fast50 in 2023 and backed by Microsoft, Google and Octopus Ventures, we’re trusted by leading law firms and in-house legal teams, including A&O Shearman, Dentons, Deloitte, and Barclays, to streamline their workflows and mitigate risks.

Data Privacy Notice

‍By submitting your application, you agree that DEFEYENE LEGAL SOLUTIONS LIMITED ('Definely') may collect, process, and store your personal data as part of our recruitment process. We will use the information you provide to assess your qualifications for the role you are applying for and to communicate with you regarding your application.Your personal data will be stored for up to 12 months, after which it will be securely deleted unless we have another lawful basis to retain it. You have the right to access, correct, or request the deletion of your data at any time.For more details on how we handle your personal data and your rights, please send us an email to [email protected] and we will send your our privacy policy.

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If you have any concerns about how your data is being processed, please do not hesitate to contact us.