As a Principal React Engineer you will be the technical leader driving the architecture and delivery of enterprise-scale web applications. This role goes beyond coding, you’ll define front-end strategy, set engineering standards, and influence product direction. You’ll design highly performant, resilient, and accessible user interfaces while mentoring teams and fostering a culture of technical excellence. Your expertise will shape reusable component libraries, modern development practices, and scalable solutions that power critical applications.

Reporting & Scope

Reporting to a Senior Engineering Manager, you’ll collaborate closely with multi-functional teams of product managers, UX designers, and backend engineers, to ensure seamless integration and an excellent user experience. This is an opportunity to lead innovation, solve sophisticated challenges, and make architectural decisions that impact thousands of users.

What You’ll Do

• Architect & build high-performance, cross-platform web applications that scale globally.

• Design and lead front-end project for LSEG financial market projects.

• Set the quality bar by defining front-end testing strategies, frameworks, and guardrails.

• Improve Core Web Vitals and overall rendering performance through profiling, measurement, and targeted optimization.

• Enable cross-team delivery by driving shared standards, reusable systems, and clear technical direction.

• Mentor and uplift engineers through thoughtful feedback, inclusive practices, and strong engineering fundamentals.

• Optimize the stack for cost, efficiency, developer velocity, and maintainability.

• Communicate trade-offs and technical risk effectively to product leaders and executives.

What You’ll Need to Succeed

• 10+ years of engineering experience with demonstraited ownership of large-scale, production-grade systems from design to deployment.

• Expert-level proficiency in modern front-end technologies, including React (or similar frameworks), TypeScript, and advanced state management patterns.

• Deep architectural knowledge of Backend-for-Frontend (BFF) services, micro-frontend strategies, and modular design principles.

• Strong performance optimization skills, with hands-on experience improving rendering efficiency at scale.

• Mastery of testing practices across unit, integration, and end-to-end layers.

• Solid understanding of web security, accessibility (WCAG), ensuring robust and inclusive user experiences.

• Ability to make high-impact technical decisions, backed by research and data, and communicate trade-offs clearly to both technical and non-technical collaborators.

• Proven leadership and mentoring experience, fostering engineering excellence and collaboration across complementary teams.

• Curiosity and adaptability, staying ahead of emerging technologies and applying them thoughtfully to solve complex challenges.

• Bachelor’s degree or equivalent experience in Computer Science, Engineering.

Key Responsibilities

• Lead development of React-based applications

• Architect scalable state management and component libraries

• Optimize performance, accessibility, and real-time data handling

• Collaborate on API design and integration

• Drive testing strategies and maintain code quality

• Mentor team members and champion modern practices

Core Skills & Technologies

• Frontend: React 18+, TypeScript, state management (Zustand/Redux), React Router

• Build Tools: Webpack, Vite, Babel

• Styling: SCSS, CSS Modules, CSS-in-JS

• Testing: Jest/Vitest, React Testing Library, Cypress/Playwright

• Quality: ESLint, Code , Git hooks

• Real-Time: WebSockets, REST APIs, GraphQL (plus)

• DevOps: CI/CD pipelines, Docker, Storybook

Preferred Experience

• Component libraries, design systems, micro-frontends.

• An understanding of financial markets.

• Java Spring boot for the BFF.

Benefits

• Work with elite global and diverse engineering teams located in Singapore, Bangkok, London, New York and Bucharest.

• Hands-on experience with FX trading platforms handling high transaction volumes.

• Exposure to high-performance, latency-intensive systems where speed and performance are critical.

• Opportunity to develop techno-functional expertise bridging technology and finance.

• Professional development through collaboration with industry experts and latest technologies.

Career Stage:

London Stock Exchange Group (LSEG) Information:

Join us and be part of a team that values innovation, quality, and continuous improvement. If you're ready to take your career to the next level and make a significant impact, we'd love to hear from you.

LSEG is a leading global financial markets infrastructure and data provider. Our purpose is driving financial stability, empowering economies and enabling customers to create sustainable growth.

Our purpose is the foundation on which our culture is built. Our values of Integrity, Partnership, Excellence and Change underpin our purpose and set the standard for everything we do, every day. They go to the heart of who we are and guide our decision making and everyday actions.

Working with us means that you will be part of a dynamic organisation of 25,000 people across 65 countries. However, we will value your individuality and enable you to bring your true self to work so you can help enrich our diverse workforce.

We are proud to be an equal opportunities employer. This means that we do not discriminate on the basis of anyone’s race, religion, colour, national origin, gender, sexual orientation, gender identity, gender expression, age, marital status, veteran status, pregnancy or disability, or any other basis protected under applicable law. Conforming with applicable law, we can reasonably accommodate applicants' and employees' religious practices and beliefs, as well as mental health or physical disability needs.

You will be part of a collaborative and creative culture where we encourage new ideas. We are committed to sustainability across our global business and we are proud to partner with our customers to help them meet their sustainability objectives. Our charity, the LSEG Foundation provides charitable grants to community groups that help people access economic opportunities and build a secure future with financial independence. Colleagues can get involved through fundraising and volunteering.

LSEG offers a range of tailored benefits and support, including healthcare, retirement planning, paid volunteering days and wellbeing initiatives.

Please take a moment to read this privacy notice carefully, as it describes what personal information London Stock Exchange Group (LSEG) (we) may hold about you, what it’s used for, and how it’s obtained, your rights and how to contact us as a data subject.

If you are submitting as a Recruitment Agency Partner, it is essential and your responsibility to ensure that candidates applying to LSEG are aware of this privacy notice.

Location: THA-Bangkok-One Bangkok

Time Type: Full time