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