Senior Frontend Developer

📍 Portugal or European Union | Remote / Hybrid We are looking for a Senior Frontend Developer to design, build and maintain modern, responsive and scalable frontend applications for enterprise-grade digital platforms. This role is suited for an experienced frontend engineer with strong expertise in JavaScript, React and Next.js, capable of delivering high-quality user interfaces in complex project environments. The focus is on building frontend solutions that are clean, performant, maintainable and aligned with solid engineering standards. What you will do Develop modern web applications using JavaScript, React and Next.js Build responsive, accessible and user-friendly interfaces using HTML5 and CSS3 Translate business and functional requirements into robust frontend solutions Collaborate with backend developers, UX/UI teams, QA, architects and project stakeholders Contribute to frontend architecture decisions and reusable component design Ensure application performance, scalability and maintainability Integrate frontend applications with APIs and backend services Participate in code reviews, technical discussions and estimation activities Apply good engineering practices, including testing, documentation and version control Troubleshoot issues and support continuous improvement of existing applications Work in Agile delivery environments, including Scrum or Kanban What we are looking for Senior-level experience as a Frontend Developer Minimum 7 years of professional experience in frontend development Strong knowledge of JavaScript Solid hands-on experience with React Solid hands-on experience with Next.js Strong knowledge of HTML5 and CSS3 Experience building responsive and cross-browser web applications Good understanding of frontend performance and optimisation techniques Experience integrating frontend applications with REST APIs or similar services Ability to write clean, maintainable and reusable code Experience with Git and collaborative development workflows Good problem-solving skills and attention to detail Ability to work with technical and non-technical stakeholders Fluent English Mandatory skills JavaScript React Next.js HTML5 CSS3 Azure Nice to have Experience with Azure-based applications or cloud-hosted frontend solutions Experience with TypeScript Experience with unit testing and frontend testing frameworks Familiarity with CI/CD pipelines Experience with design systems or component libraries Knowledge of accessibility standards Experience in enterprise, e-commerce, retail or large-scale digital platforms What we offer 20 dedicated learning and development days per year Support for relevant certifications and technical development Growth in frontend engineering and technical leadership Close collaboration with senior engineers, architects and consultants Challenging projects where usability, performance and maintainability matter 💡 We are looking for frontend developers who understand that good interfaces are not only visual. They are engineered, tested, maintained and built to last. Who we are | XScience XScience is a technology partner focused on building enterprise-grade digital, data and analytical solutions. We work with organisations that demand technical rigour, predictability and well-founded decisions. We operate at the intersection of engineering, architecture and business, helping our clients turn technology into reliable, scalable and maintainable systems. We favour solid approaches, mature technologies and engineering practices that stand the test of time. We are looking for professionals who think long term, challenge fragile solutions and value well-engineered systems.