Senior Software Engineer (React)

Cornerstone VC; City of London; On-site; GBP 60,000 - 80,000; Full time

Job summary

A leading legal technology firm in London is looking for a Senior Engineer to develop sophisticated React applications integrated with Microsoft Office products. The ideal candidate has 4+ years of experience and a strong proficiency in web technologies. This hybrid role offers a competitive salary, equity opportunities, and various benefits including annual learning budgets and private healthcare.

Benefits

Competitive salary & annual bonus

Equity in the company

Quarterly team socials & annual company offsite

Hybrid working (Tues & Thurs in-office)

25 days holiday + bank holidays

£750 annual learning & development budget

Private healthcare (incl. dental & optical)

Enhanced parental leave

Qualifications

• 4+ years of hands-on experience building production React applications.
• Strong proficiency in React, TypeScript, JavaScript, HTML, and CSS.
• Experience integrating with Microsoft Office, especially Office.js.

Responsibilities

• Design and build sophisticated React applications integrating with Microsoft Office.
• Write clean, scalable, maintainable code while driving performance.
• Mentor and support team members through knowledge sharing.

Skills

React

TypeScript

JavaScript

HTML

CSS

Microsoft Office integration

Excellent communication

Git

Performance optimization

Job description

Location

London

Employment Type

Full time

Location Type

Hybrid

Department

Technology

About the role

We’re looking for a Senior Engineer with strong technical depth and a passion for building exceptional user experiences. You’ll play a key role in shaping our front-end architecture, collaborating closely with product and design teams, and delivering scalable, performant solutions used by legal professionals worldwide.

As a senior member of the team, you’ll act as a technical expert and a trusted partner helping to guide best practices, influence decisions, and mentor others through collaboration and example.

What you’ll do:

• Design and build sophisticated React applications integrating with Microsoft Word, M365, and other Office products using Office.js.

• Write clean, scalable, and maintainable code while driving performance and reliability.

• Collaborate with product, design, and engineering teams to deliver user-focused, accessible features.

• Contribute to architectural discussions and help shape the evolution of our tech stack.

• Mentor and support team members through knowledge sharing, code reviews, and best practice guidance.

• Troubleshoot complex technical challenges and drive continuous improvement through automation and AI-assisted workflows.

• Maintain high-quality standards with robust testing, documentation, and security practices.

What you’ll bring:

• 4+ years of hands‑on experience building production React applications.

• Strong proficiency in React, TypeScript, JavaScript, HTML, CSS, and modern web technologies.

• Experience integrating with Microsoft Office, especially Office.js and Word add‑ins.

• Familiarity with agentic coding assistants such as Claude Code or similar AI tools.

• Excellent communication and collaboration skills in English.

• Proven ability to work independently while contributing effectively to team goals.

• Experience working successfully in hybrid or remote development environments.

• Solid understanding of React performance optimisation (e.g. memoisation, code splitting, avoiding unnecessary re‑renders).

• Experience with Git, version control best practices, and CI/CD pipelines.

We’ll be lucky if you have:

• Knowledge of Microsoft Office Add‑in guidelines and Office Store submission processes.

• Experience optimising in‑browser text editors for speed and responsiveness.

• Prior experience in product‑focused or startup environments.

• Exposure to AI‑powered developer tools and automation 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 [e-mail] and we will send you our privacy policy.

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