Principal Software Engineer

Principal Software Engineer | Front End (React) | London, Hybrid

Our client is a forward-thinking global firm redefining the future of finance through technology.

They are looking for a Principal React Engineer who can set the technical direction for the front-end, champion best practices, and still enjoy being hands-on.

Someone who obsesses over clean design, performance and scalability, and is comfortable leading from the front.

The Opportunity

You'll be the go-to technical leader for front-end engineering within a cross-functional product team, shaping the architecture, tooling and standards for user-facing applications used by investment professionals across the business.

The team is currently re-architecting its stack to be fully cloud-native (AWS), with React and TypeScript on the front end and Python-based services on the backend.

You'll work in a culture that values engineering excellence – TDD, clean code, pair programming, thoughtful code reviews – and your voice will carry weight in how the platform evolves.

What You'll Do

• Lead the design and development of complex, high-performance React applications using React, TypeScript and modern front-end libraries.
• Define and drive front-end architecture, standards and best practices, ensuring quality, consistency and reusability across products.
• Collaborate closely with Backend, UX and Product to refine user journeys, ensuring interfaces are intuitive, performant and accessible.
• Partner with portfolio managers, researchers and analysts to translate complex domain problems into elegant, user-focused solutions.
• Mentor and coach other engineers, raising the bar on code quality, testing and delivery discipline.
• Contribute to the evolution of a cloud-native architecture on AWS, working closely with backend and platform teams.

Location: London City, hybrid working (3 days per week in the office)

Package: Highly competitive base + bonus + benefits

What You'll Bring

• Significant experience building large-scale React and TypeScript applications, ideally in complex or data-heavy domains.
• Experience within Financial Services environments is highly advantageous e.g. Investment banking, trading, asset management, etc.
• Deep knowledge of React, TypeScript, state management (e.g. Redux or similar), Apollo Client and GraphQL/REST APIs.
• Experience in cloud-native environments (AWS or Azure), and how front-end and backend services fit together in distributed systems.
• Strong understanding of front-end performance optimisation, including data streaming (WebSockets, server-sent events, chunked responses).
• Solid experience with testing strategies (unit, integration, E2E) – Playwright, Cypress or similar tools a plus.
• Bonus points for experience with design systems (e.g. Material UI) and data visualisation libraries.

About You

• A hands-on technical leader who's comfortable making architectural decisions and backing them up with code.
• Confident owning front-end initiatives end-to-end, from discovery and design through to delivery and optimisation.
• Collaborative and pragmatic - able to work across product, UX and engineering teams without ego.
• Curious, always learning, and keen to improve both the codebase and the way the team works.

If you are interested in this Principal Software Engineering Role, please respond to this advert directly with your updated CV or email it to chantelle.smith@sourcegroupinternational.com