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

Blu Selection; Barcelona; Híbrido; EUR 50.000 - 70.000; Jornada completa

Descripción de la vacante

A technology recruitment agency based in Barcelona is seeking a Senior Full Stack Developer to enhance a new web platform. The ideal candidate will have over 5 years of experience with strong proficiency in React.js and Next.js, as well as advanced skills in JavaScript and TypeScript. This role offers a full-time freelance contract with a fixed daily rate of €525 in a hybrid work environment, making it a compelling opportunity for skilled developers.

Servicios

Fixed daily rate of €525

Full-time freelance mission

Renewable 3-month contract

Formación

• 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.

Responsabilidades

• Develop and maintain complex user interfaces using React and Next.js.
• Design and integrate REST APIs and WebSocket endpoints.
• Write unit and integration tests using Jest and Testing Library.

Conocimientos

React.js

Next.js

JavaScript

TypeScript

Node.js

REST APIs

Jest

Testing Library

Docker

Herramientas

Confluence

AWS ECR/EKS

OpenShift

Descripción del empleo

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.

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

• 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

• Full-time freelance mission

• Fixed daily rate: €525/day

• 3-month contract, renewable depending on performance and roadmap

• Hybrid environment from Barcelona