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 #J-18808-Ljbffr

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