Frontend Engineer

Frontend Engineer

Marfeel is a publishing intelligence platform trusted by over 5,000 publishers worldwide: including Business Insider, Le Figaro, El País and McClatchy. We help publishers turn data into action: understanding what content is working right now, what has performed over time, and what to do next. Our platform gives editorial, SEO, audience, and revenue teams a unified view of their business, spanning real-time dashboards and deep historical analysis, all in one place.

Our international team is made up of over 15 different nationalities, with headquarters in Barcelona. Our people and our diversity are at the heart of what we build, and we are still growing.

We are looking for a Frontend Engineer with a strong foundation in JavaScript and a sharp eye for performance. You will build the interfaces that bring our analytics platform to life: writing clean, performant JavaScript from first principles and creating interactive components for publishers around the world. You use AI coding tools as a core part of how you work, and you are excited about what that unlocks. You will work in a collaborative team environment alongside backend developers, UX designers and product managers, and you will have real ownership over the frontend code you write.

This is what you will do:

• Write clean, well-structured JavaScript and CSS across all modern browsers
• Write vanilla JavaScript where appropriate: you reach for the framework when it adds value, not by default
• Build interactive, high-performance UI components using React and TypeScript
• Create and maintain a component library using Storybook and styled-components
• Collaborate with UX designers to implement pixel-accurate, intuitive interfaces
• Work on performance: scroll, rendering, load times and jank are things you care about
• Contribute to frontend architecture decisions and coding standards
• Work in an Agile environment with short, focused sprints

This is you:

• 5+ years of experience building frontend applications at web scale
• Strong vanilla JavaScript skills: you write clean, framework-independent JS and understand the language deeply, not just the abstractions on top of it
• Proficiency in TypeScript and React
• You use AI coding tools: Claude Code, Cursor, Copilot or similar, as a natural part of your development workflow, not as an afterthought
• Solid understanding of HTML5, CSS and cross-browser development
• Deep understanding of browser performance: rendering, caching, scroll performance, junk and paint cycles
• Solid experience with UI component architecture and design systems
• Familiar with end-to-end and integration testing (Jest or similar)
• You care about code quality: pair programming, TDD, collective ownership and iterative delivery are part of how you work
• You speak Spanish and English

We will be impressed by experience in:

• Recent web platform APIs: Web Animation API, Web Workers, CSS 3D transformations, ES2020+
• Experience with large-scale cloud-deployed web applications
• Experience integrating AI tooling into development workflows in a meaningful way: using agents, MCP servers, or AI-assisted development at team level
• Familiarity with CI/CD workflows and tools such as Jenkins, GitHub Actions or Docker
• An interest in data visualization and working with real-time data in the UI
• UX design sensibility or experience collaborating closely with designers
• Active contributions to open-source projects

This will be you as part of the Marfeel team:

• Work on product that reaches publishers and newsrooms globally
• Option to work full remote, hybrid or office-based (if in BCN area)
• Support with home office equipment
• Flexible hours and early finish on Fridays
• Subsidized health insurance for you and your partner/family (Adeslas)
• Subsidized monthly plan to a large network of health and wellness centers (Wellhub)
• Transport, restaurant and kindergarten tickets (Cobee)
• Free language classes (English/Spanish)
• Open-space, light-filled and eco-conscious office with large sunny terrace (if BCN based)
• Unlimited refreshments including coffee, tea and soft drinks at the office (if BCN based)
• Loyalty vacation days
• Access to training platforms, courses and materials
• Referral bonus for talent brought to us by you

Our interview process:

• Phone call: covering the basics to make sure we are a good fit for each other
• Technical and personal interview: understanding you professionally and personally, and answering all your questions
• Test stage: a preview of the type of work, so you can see us in action too
• Test review interview: we discuss your test and provide feedback