Senior Frontend Engineer - SDK & Authentication

About the role

LSEG (London Stock Exchange Group) is looking for a Senior Frontend Developer to join its Customers Identity & Access Management team. You will maintain and evolve a JavaScript SDK that enables secure authentication and integrates the company's authentication into client applications. The role suits someone who enjoys developer experience, SDK design and security-focused frontend engineering.

Key responsibilities

• Own and maintain a JavaScript SDK built with React and TypeScript, integrating securely with a custom Secure Token Service.
• Design intuitive, developer-friendly APIs that abstract complex authentication flows (OAuth2, OpenID Connect).
• Keep the SDK secure, performant and easy to integrate across many frontend applications.
• Work with backend engineers to align SDK functionality with evolving identity protocols and token flows.
• Build automated tests and CI pipelines to ensure quality, reliability and backward compatibility.
• Write clear documentation and sample apps for internal and external developers.
• Stay up to date with frontend security best practices and contribute to platform-wide improvements.

Required profile

• 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 SDK versioning strategies.
• Experience with frontend performance optimization, cross-browser compatibility and accessibility standards.
• Passion for clean code, automation and continuous improvement, and excellent interpersonal skills.

What we offer

• Competitive compensation with performance-based rewards.
• A flexible hybrid work model.
• Access to cutting-edge tools and infrastructure.
• Continuous learning, including certifications, conferences and internal mobility.
• A collaborative culture and the chance to work on a globally critical system.