Staff Software Engineer

Definely is building AI-powered tools that transform how legal professionals work. Our platform processes a large volume of complex legal documents, and the engineering behind it needs to be robust, scalable, and thoughtfully designed; across the entire stack.

We're looking for a Staff Software Engineer who is genuinely strong across the full stack; someone with real architectural opinions on both the frontend and backend, and the hands-on ability to act on them. This isn't a role for someone who leans heavily on one side of the stack. You'll be expected to make good technical decisions end-to-end, from how we structure React components and manage state on the frontend, through to how we design services, data pipelines, and backend systems that process documents at scale.

This role is deeply hands-on. You’ll be writing and reviewing code every day, while also raising the engineering bar across the team through strong technical leadership, mentoring, and good architectural judgment. Language background matters less than engineering depth: we use Python, TypeScript, and C#/.NET across the stack, and we care far more about how you think and build than which language you reach for.

As a Staff Engineer you'll be hands on and deeply involved in the hardest engineering problems we face:

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  Design and build across the full stack - from React-based frontend systems to backend services and data pipelines; taking end-to-end ownership of technical decisions

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  Architect scalable, reliable systems capable of processing large volumes of complex legal documents, and help the team understand and apply the right patterns

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  Lead technical design and architecture discussions, making well-reasoned decisions and building consensus across the engineering team

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  Write, review, and ship production code regularly. This is a hands-on IC role and you'll be in the codebase every day

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  Help set and uphold high engineering standards across both frontend and backend, through code review, documentation, and direct collaboration

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  Mentor engineers across the team, helping them grow their technical depth and make better decisions

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  Identify and proactively address technical debt, reliability risks, and architectural weaknesses before they become problems

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  Collaborate closely with product, design, and other engineering leads to shape what we build and how we build it

• Genuine full-stack capability. You have real architectural opinions and experience on both the frontend and backend, and can lead technical decisions on either side

• Strong backend engineering fundamentals. Experience designing distributed systems, APIs, and data-intensive services that run reliably in production at scale

• Experience with high-throughput data processing. You've built or operated systems that process large volumes of data reliably, and understand the tradeoffs involved

• Language flexibility. You're fluent in at least one of Python, TypeScript (including React), or C#, and comfortable picking up others; we care about engineering depth, not language loyalty

• A track record of technical leadership as a senior IC. You've influenced architecture and raised standards without needing a management title

• Strong communication and collaboration skills. You can articulate technical decisions clearly, build alignment, and work well with engineers, product managers, and designers

• High standards and low ego. You hold the bar high in code review and architectural discussions, but you're collaborative and genuinely enjoy helping others improve

• Have experience in legaltech, document processing, or other complex document-heavy domains

• Have worked with AI/ML-powered products and understand how to build robust systems around them

• Have experience with Elasticsearch, vector databases, or large-scale document indexing

• Have C#/.NET experience. We have significant .NET in our stack and depth here is genuinely valued

• Have led or contributed to significant architectural migrations or platform modernisation projects

• 💰 Competitive salary & annual bonus based on performance

• 📈 Equity in Definely

• 🎉 Quarterly team socials + holiday parties

• 🏠 Hybrid working + 🌍 1 month “work from anywhere”

• 🏖️ 25 days holiday + bank holidays

• 🎂 Take your birthday off

• 📚 £750 annual learning & development budget

• 🩺 Private healthcare (incl. dental & optical)

• 👶 Enhanced parental leave + Workplace Nursery salary sacrifice scheme

• 🚲 Additional perks: Cycle to Work

• 💻 Top-quality equipment

At Definely, we’re building the Review layer for legal work in the age of AI.

As AI transforms how contracts are drafted, the challenge is no longer just generation, it’s verification. Lawyers remain accountable for what goes out the door, but the volume and complexity of AI-generated work is pushing traditional review to its limits.

Definely gives lawyers a structured way to understand and verify complex agreements, modelling contracts as systems of definitions, cross-references, and dependencies, surfacing hidden risks and making review more rigorous and defensible.

Trusted by leading law firms and global enterprises, including A&O Shearman, Slaughter and May, BP, and Barclays, we integrate directly into the tools lawyers already use.

We recently raised our Series B and are backed by Microsoft, Google, and Octopus Ventures. This is a rare opportunity to shape a new category at the moment it becomes essential.

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 people@definely.com and we will send you 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.