Freelance Senior OR Junior Full Stack Developer – React / Next.js / Node.js – BarcelonaYou 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.
ResponsibilitiesDevelop and maintain complex, data-heavy user interfaces usingReact and Next.js
Build and optimisereusable componentsand contribute to the internal UI library
Design and integrateREST APIsand WebSocket endpoints
Ensure code quality throughclean architecture and best practices
Writeunit 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 Qualifications3-5+ years of experienceas a Full Stack or Front-End Engineer
Strong hands-on experience withReact.js and Next.js
Experience building and consumingREST APIs




Good understanding of backend technologies (Node.js required; Python/FastAPI is a plus)
Experience withcomponent 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 HaveExperience 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 OfferFull-time freelance mission
3-month contract, renewable depending on performance and roadmap
Hybrid environment from Barcelona
Seniority levelMid-Senior level
Employment typeFull-time
Job functionInformation Technology
IndustriesPharmaceutical Manufacturing
Barcelona, Catalonia, Spain
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📌 Freelance Senior Or Junior Full Stack Developer - React / Next.Js / Node.Js - Barcelona
🏢 Blu Selection Recruitment Agency
📍 Barcelona