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

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