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Urgent! Principal Full Stack Software Engineer Job Opening In Madrid – Now Hiring SGS

Principal Full Stack Software Engineer



Job description

Job Description

This is a role for a product-minded engineer who believes that world-class user experiences are built on a foundation of world-class code.

You won't just be building features; you'll be crafting entire products, from the database to the user interface. This is a role with massive leverage.

As our foundational Principal Full Stack Engineer, your mission is to own the end-to-end development of our flagship digital products.

You will lead the development of our most ambitious web applications while simultaneously building and championing a comprehensive library of reusable components and patterns (both frontend and backend).

Your goal is to create beautiful, fast, and accessible user interfaces powered by scalable and resilient backend services, and to empower all teams to do the same.

What You'll Build and Own

  • Lead Frontend Architecture: Design and implement the technical architecture for complex, data-rich, and highly interactive web applications, including backend services, APIs, and frontend structure.

  • Own the Component & Pattern Library: Build, maintain, and evangelize our central component library and design system (, using Storybook), as well as reusable backend patterns, ensuring consistency and quality across all products.

  • Build End-to-End Products: Act as the lead hands-on developer for our most critical products, setting the bar for code quality, performance, and user experience across the entire stack.

  • Be the Voice of the User: Partner closely with product and design to translate user needs into elegant and effective technical solutions.
  • Optimize for Developer Velocity: Own the full stack build tooling, testing strategies, and monorepo structure to create a fast, modern, and enjoyable development environment for all engineers.
  • Qualifications

  • Frontend Expertise: Expert-level proficiency in React and TypeScript.

    Deep experience building and scaling complex single-page applications.
  • Backend Expertise: Proven experience building and shipping backend services and APIs using a modern stack (, , Go, or Python) and working with databases like PostgreSQL.

  • Design Systems & Tooling: Proven experience building and maintaining a component library from the ground up using tools like Storybook and Chromatic.
  • Modern Web Stack: Mastery of modern CSS (, CSS-in-JS, Tailwind CSS), web accessibility (WCAG), and frontend performance optimization techniques.
  • Engineering & DevOps: Expertise with modern build tools (Vite, Webpack), testing frameworks (Jest, Cypress, Playwright), and monorepo management (Nx, Turborepo).
  • Who You Are

  • You are a seasoned software engineer (8+ years) with a deep passion for building great products, from the API to the UI.

  • You are a pixel-perfect builder who is also pragmatic and understands the need to ship.
  • You have a product mindset, viewing your fellow developers as customers of the tools and libraries you create.
  • You are an excellent communicator who can articulate technical decisions and advocate for both the user and the developer.

  • Required Skill Profession

    Computer Occupations



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