Staff React Engineer

Sorry, this job was removed at 12:34 p.m. (CST) on Friday, Jan 09, 2026
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London, Greater London, England
In-Office
Legal Tech • Software
The Role
About the role

Following our recent $30M Series B funding, we're expanding the team to accelerate development of our legal technology products that integrate with Microsoft products through Office.js.

We're looking for a Staff Engineer to guide two mid-senior React developers who will look to you for architectural guidance and technical direction.

As the technical side of the product Triad, your technical decisions will directly shape product direction.

What you'll do:
  • Lead and mentor a team of React developers, fostering collaboration, growth, and high coding standards

  • Architect and develop complex React applications integrated with Microsoft Word, M365, and Word Online using Office.js

  • Write clean, efficient, and maintainable code while ensuring scalable, high-performance solutions

  • Collaborate with cross-functional teams to deliver innovative, user-centric, and accessible features

  • Optimise application performance and responsiveness, overcoming Office.js limitations creatively

  • Establish strong testing, debugging, and documentation practices to maintain quality and reliability

  • Implement security best practices to protect user data and maintain system integrity

  • Troubleshoot complex technical issues and contribute to architectural decisions and tech-stack evolution

  • Enhance developer productivity through tooling, automation, and AI-assisted coding

What you'll bring:
  • Minimum 5 years of hands-on, product-focused experience with React development

  • Proven leadership experience in software development teams

  • Expert-level proficiency in React, TypeScript, JavaScript, HTML, CSS, and modern web technologies

  • Strong experience with Microsoft Office integration, particularly Office.js and Word add-ins

  • Experience with agentic coding assistants such as Claude Code

  • Excellent English communication skills, both written and verbal

  • Demonstrated ability to work autonomously while providing clear direction to others

  • Extensive experience working effectively in remote environments

  • Passion for knowledge sharing and helping team members grow

  • Know how to optimize React apps (prevent useless re-rendering, memoization, code splitting etc)

  • Strong grasp of Git, version control best practices, and CI/CD pipelines.

  • Excellent problem-solving, communication, and collaboration skills.

  • Ability to work effectively in a fast-paced, agile environment.

We'll be lucky if you have:
  • Knowledge of Microsoft Office Add-in guidelines and Office Store submission processes

  • Background in LegalTech or professional services software

  • Previous experience working with in-browser text editors, specially if you were part of optimization efforts to make the experience snappier.

  • Experience in product-focused or startup environments.

  • Exposure to other AI-powered developer tools and workflows.

What we offer:
  • 💰 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

‍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 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.


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

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The Company
HQ: London
62 Employees
Year Founded: 2017

What We Do

Named as one of the 50 fastest growing tech companies in the UK by Deloitte in 2023, Definely addresses the number one issue associated with drafting, reviewing and understanding legal documents. With Definely, you no longer need to ctrl+f, print out a legal document or scroll endlessly just to access the information (defined terms and cross-references) you need to understand the clause or provision being reviewed. Delivered as an MS Word Plugin, Definely is easy to use, integrates effortlessly into your current workflows and does not require any complex IT processes to get up and running.

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