Senior Software Engineer - Frontend

We're looking for a Senior Software Engineer with strong frontend expertise to join our Sage HCM engineering team in Barcelona. You'll work across a large-scale, modular enterprise product at an interesting inflection point: our core system is built on Sencha Ext JS (7.5+), and we are actively introducing React for new functional modules and high-performance UI components. This is not a role for someone who wants to work in a single framework. You'll maintain and enhance a robust Ext JS foundation whilst building new capabilities in React, integrating the Carbon Sage Design System, and ensuring seamless interaction between the two. If you enjoy the technical challenge of working across a hybrid architecture at enterprise scale - and care deeply about code quality and user experience - this role will suit you well. This is a hybrid role requiring 3 days per week in our Barcelona office. First 90 Days • 30 Days: Familiarise yourself with the Sage HCM frontend architecture: the Ext JS codebase, the React modules in development, the Carbon Design System integration, and the team's engineering practices. Meet your colleagues across frontend, backend, QA, and product. Begin contributing to active sprint work - bug fixes, small features, and code reviews - to build context quickly. • 60 Days: Take ownership of frontend delivery for your assigned areas. Contribute meaningfully to React-based feature development and Ext JS maintenance. Engage with Figma designs and work closely with backend engineers on API integration. Begin identifying opportunities to improve performance, code quality, or the hybrid integration between the two frameworks. • 90 Days: Deliver end-to-end frontend features independently, from design translation through to production. Contribute to architectural decisions around the React/Ext JS hybrid approach. Share your knowledge with the team and be an active voice on frontend best practices, Carbon implementation standards, and performance optimisation. Meet the Team You'll join a cross-functional Sage HCM engineering team that includes frontend and backend engineers, QA, solution designers, and product owners. The team operates in an Agile environment and has a strong culture of engineering quality and collaborative delivery. The dual-framework architecture reflects the reality of evolving a large, mature product: Ext JS underpins a significant portion of the system that continues to serve customers well, whilst React enables the team to build new capabilities with modern tooling and design system consistency. You'll be working at the boundary between the two - which requires both technical depth and pragmatic judgement. How Success Will Be Measured • Quality, maintainability, and performance of the frontend code you deliver across both frameworks • Consistent and accurate implementation of the Carbon Design System in new development • Smooth integration between React components and the existing Ext JS environment • Timely and reliable contribution to team sprint goals and release deliverables • Positive collaboration with backend, QA, and product colleagues