Freelance Senior OR Junior Full Stack Developer – React / Next.js / Node.js – Barcelona You will collaborate closely with the Tech Lead, Product Owner, UX Designer, and Data team to design, develop, and deliver high-quality features within an agile environment. Responsibilities
* Develop and maintain complex, data-heavy user interfaces using React and Next.js
* Build and optimise reusable components and contribute to the internal UI library
* Design and integrate REST APIs and WebSocket endpoints
* Ensure code quality through clean architecture and best practices
* Write unit and integration tests (Jest / Testing Library)
* Collaborate with Product, UX, and Data to deliver features end-to-end
* Participate in architecture discussions and decision-making
* Troubleshoot and resolve issues across the stack
* Contribute to CI/CD processes and development workflow improvements
* Maintain documentation on Confluence Required Qualifications
* 3-5+ years of experience as a Full Stack or Front-End Engineer
* Strong hands-on experience with React.js and Next.js
* Experience building and consuming REST APIs




* Good understanding of backend technologies (Node.js required; Python/FastAPI is a plus)
* Experience with component libraries, design systems, or shared UI components
* Familiarity with modern testing frameworks (Jest, Testing Library)
* Good understanding of performance, security, and scalability principles
* Comfortable working in cross-functional agile teams
* Strong communication skills in English Nice to Have
* Experience with container technologies (Docker, AWS ECR/EKS, OpenShift)
* Experience with CI/CD pipelines
* Knowledge of SonarQube, Checkmarx, or similar code quality tools
* Experience in healthcare, pharma, or other regulated environments

What We Offer
* Full-time freelance mission
* 3-month contract, renewable depending on performance and roadmap
* Hybrid environment from Barcelona Seniority level Mid-Senior level Employment type Full-time Job function Information Technology Industries Pharmaceutical Manufacturing Barcelona, Catalonia, Spain

📌 Freelance Senior OR Junior Full Stack Developer – React (Barcelona)
🏢 Blu Selection Recruitment Agency
📍 Barcelona