Location
Paternoster Square, London

Hours
Full Time

Salary
Negotiable

About the Role
Join London Stock Exchange Group (LSEG) as a Senior Frontend Engineer within our Customers Identity & Access Management team. You will play a pivotal role in maintaining and evolving our JavaScript SDK, a critical interface enabling secure authentication and seamless integration of our Authentication services into client applications. This role is ideal for someone passionate about developer experience, SDK design, and security-focused frontend engineering.

You will own and maintain a JavaScript SDK built with React and TypeScript, enabling secure integration with our custom Secure Token Service. You will design intuitive, developer-friendly APIs that abstract complex authentication flows such as OAuth2 and OpenID Connect. Ensuring the SDK is secure, performant, and easy to integrate across a wide range of frontend applications will be key. Collaboration with backend engineers to align SDK functionality with evolving identity protocols and token flows is essential.

Additional responsibilities include building automated tests and CI pipelines to ensure quality, reliability, and backward compatibility, writing clear documentation and sample applications to support internal and external developers, and staying current with frontend security best practices to contribute to platform-wide improvements.

LSEG is a global financial markets infrastructure and data business with over 300 years of history, operating in 65 countries and employing 25,000 people worldwide. We are committed to integrity, partnership, excellence, and change, fostering an inclusive culture where everyone can grow and fulfil their potential.

Experience
- Proven experience in frontend development with deep expertise in React, TypeScript, and modern JavaScript.
- Experience designing and maintaining SDKs or libraries used by other developers.
- Strong understanding of OAuth2, OpenID Connect, and secure authentication flows.
- Familiarity with CI/CD pipelines, automated testing, and versioning strategies for SDKs.
- Experience with frontend performance optimization, cross-browser compatibility, and accessibility standards.

About you
- Passionate about clean code, automation, and continuous improvement.
- Excellent interpersonal skills with a strong focus on developer experience and security.
- Collaborative mindset and ability to work effectively within cross-functional teams.

Qualifications
- Relevant technical qualifications are advantageous but not mandatory; a strong track record and passion for frontend engineering and security are essential.