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.JsBuild and optimisereusable componentsand contribute to the internal UI libraryDesign and integrateREST APIsand WebSocket endpointsEnsure code quality throughclean architecture and best practicesWriteunit and integration tests(Jest / Testing Library)Collaborate with Product, UX, and Data to deliver features end-to-endParticipate in architecture discussions and decision-makingTroubleshoot and resolve issues across the stackContribute to CI/CD processes and development workflow improvementsMaintain documentation on ConfluenceRequired Qualifications~3-5+ 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 EnglishNice to HaveExperience with container technologies ( Docker, AWS ECR/EKS, OpenShift)Experience with CI/CD pipelinesKnowledge of SonarQube, Checkmarx, or similar code quality toolsExperience in healthcare, pharma, or other regulated environmentsWhat We Offer~ Full-time freelance mission~3-month contract, renewable depending on performance and roadmap~ Hybrid environment from BarcelonaSeniority levelMid-Senior levelEmployment typeFull-timeJob functionInformation TechnologyIndustriesPharmaceutical ManufacturingBarcelona, Catalonia, Spain#J-18808-Ljbffr

📌 Senior Fullstack Developer (React, Node.Js, Next.Js) (Madrid)
🏢 Blu Selection Recruitment Agency
📍 Madrid