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 that enables secure authentication and seamless integration of our Authentication into client applications across our customers. 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. You will build automated tests and CI pipelines to ensure quality, reliability, and backward compatibility. Additionally, you will write clear documentation and sample applications to support both internal and external developers. Staying current with frontend security best practices and contributing to platform-wide improvements is expected.

At LSEG, you will be part of a high-performing team where your expertise is valued and your impact is visible. We offer a flexible hybrid work model, access to cutting-edge tools, continuous learning opportunities, and a collaborative culture that values technical mastery, ownership, and innovation. This is your chance to work on a globally critical system that powers secure financial transactions across markets.

Experience
- Proven experience in frontend development with deep expertise in React, TypeScript, and modern JavaScript.
- Demonstrated 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 with the ability to work effectively across teams and disciplines.

Qualifications
- No specific formal qualifications required; however, relevant experience and a commitment to continuous learning are essential.