Freelance Senior OR Junior Full Stack Developer – React / Next.js / Node.js – Barcelona

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