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Blu Selection Logo Blu Selection · IT - Software Development

Freelance Senior Full Stack Developer

Spain, Barcelona B2B · Job Posted December 27, 2025
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Job Description

We are looking for a Senior Full Stack Developer to join our team and contribute to the development of a new web platform built with modern JavaScript technologies. 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. This role requires strong expertise in front-end engineering (React/Next.js), solid understanding of backend APIs, and the ability to write scalable, maintainable code.

Job Responsibility

  • 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

Requirements

  • 5+ years of experience as a Full Stack or Front-End Engineer
  • Strong hands-on experience with React.js and Next.js
  • Advanced knowledge of JavaScript and TypeScript
  • 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

  • Fixed daily rate: €525/day
  • 3-month contract, renewable depending on performance and roadmap
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