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
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📌 Freelance Senior OR Junior Full Stack Developer – React / Next.js / Node.js – Barcelona
🏢 Blu Selection Recruitment Agency
📍 Barcelona