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Senior Full Stack Engineer (.Net)

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Senior Full Stack Engineer (.Net)

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DefinelyAbout The Role

We’re looking for exceptionally talented Senior Full Stack Engineers with deep expertise in .NET/C# and WPF to join our growing team.About The Role

We’re looking for exceptionally talented Senior Full Stack Engineers with deep expertise in .NET/C# and WPF to join our growing team.

In this role, you will lead the full software development lifecycle: from design and implementation to testing, deployment, and ongoing support for our core LegalTech products. You’ll build and enhance rich WPF-based Windows desktop applications, scalable backend services, and cloud-integrated solutions. While the title includes “Full Stack,” this is not a traditional web development role; your focus will be on high-performance Windows applications and associated backend systems.

You’ll also play a key role in mentoring engineers, driving architectural improvements, and shaping engineering practices that ensure performance, maintainability, and innovation.

Key Responsibilities

Application Development

Architect, design, and develop complex desktop applications using WPF and modern patterns like MVVM.Build and maintain robust .NET Framework and .NET Core backend services, APIs, and libraries.Implement modular application architectures to support scalability and maintainability.Integrate with cloud platforms (AWS, Azure) for distributed computing and storage.

Technical Leadership and Collaboration

Lead design reviews, code reviews, and architectural discussions to ensure technical excellence.Collaborate with product managers, designers, and cross-functional engineers to deliver high-impact features.

Quality and Best Practices

Champion best practices including SOLID, DRY, KISS, and test-driven development (TDD) to ensure code quality and building of new features.Leverage AI-assisted tools (e.g., GitHub Copilot, Claude Code) to streamline development and accelerate feature delivery.Perform code refactoring, increase test coverage, and improve legacy codebases.Apply performance and memory profiling techniques to ensure optimal runtime behaviour.Utilise dependency injection frameworks (e.g., Autofac) to write clean and decoupled code.

Problem Solving and Innovation

Tackle complex technical challenges across frontend and backend systems.Design solutions with a strong emphasis on asynchronous programming, multithreading, and regular expression optimisation.Continuously improve system performance and developer experience through innovation and tooling.

What You Bring:

5+ years of professional experience with .NET and C# across frontend and backend development.Deep expertise in WPF, including XAML, data binding, custom controls, UI animations, and MVVM.Strong experience building Windows desktop applications with attention to UI/UX design.Proficient in both .NET Framework and .NET Core.Familiar with dependency injection, modular architectures, and reusable components.Strong understanding of multithreading, async/await, and asynchronous design patterns.Experienced with regular expressions, especially in parsing or document-focused workflows.Proven use of performance and memory profilers to debug and optimise applications.Experience working with Visual Studio, JetBrains Rider, ReSharper, and modern DevOps pipelines.Experience with AI-assisted coding tools (e.g., GitHub Copilot, Claude Code) to accelerate development.Familiar with relational databases (e.g., PostgreSQL) and RESTful APIs.Strong grasp of Git and version control best practices.Strong communication, collaboration, and problem-solving skills.Comfortable in a fast-paced, agile environment.

Nice to have:

Prior experience in product-centric or startup environments.Experience with VSTO Word Add-Ins.Exposure to other AI-powered developer tools and workflows.Familiarity with modern cross-platform frameworks like .NET MAUI, Blazor, or Avalonia.Understanding of cloud-native design, distributed systems, and DevOps best practices.

What we can offer you:

Competitive Salary

We offer a highly competitive salary that reflects your skills, experience, and contributions.

Impact and Growth

Join a fast-growing startup where your ideas matter; experiment, innovate, and see your work come to life.

High-Performance Culture

Work in a truly meritocratic environment alongside ambitious, driven professionals who push each other to excel.

Prestigious Partnerships

Collaborate with some of the world’s top law firms, financial institutions, and multinational corporations.

Prime London Location and Hybrid Flexibility

Enjoy a vibrant office in the heart of Aldgate with the option to work in a hybrid environment. We tend to come into the office 2-3 times a week, although you can come in more!

Ongoing Learning and Development

Access top-tier training, mentorship, and continuous support to advance your career.

Time Off

Enjoy 25 days of holiday per year, plus UK bank holidays, to recharge and unwind.

Pension Plan

Secure your future with our competitive pension scheme.

Private Healthcare

Access to Vitality healthcare, including dental and optical.

Flexible Working

Work in a way that suits your lifestyle, with the freedom to balance professional and personal priorities.

Enhanced Parental Leave

We support working parents with generous parental leave policies that go far beyond statutory requirements.

Cycle to Work Scheme

Save on a new bike and accessories while promoting a healthier, more sustainable commute.

Workplace Nursery Scheme

Saving working parents lots of money through our salary sacrifice scheme!

Top-Quality Equipment

Get the tools you need to perform at your best, from cutting-edge tech to ergonomic office setups.

About Definely

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 AandO 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

hr@definely.com

and we will send your our privacy policy.

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

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