> Markdown version of [/jobs/ext/3398538-frontend-engineer](https://www.wearedevelopers.com/jobs/ext/3398538-frontend-engineer). Every page supports `.md` or `Accept: text/markdown`. Links point to the HTML versions so they work for humans too. Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Frontend Engineer - **Company:** APEXX Global - **Location:** Madrid, Spain (Remote available) - **Contract:** Permanent contract - **Skills:** HTML, JavaScript (Programming Language), Application Programming Interfaces (APIs), Automation of Tests, Big Data, Cascading Style Sheets (CSS), Cross-Origin Resource Sharing (Ajax Programming), Data Visualization, Software Debugging, Node.Js, PCI Data Security Standards, Performance Tuning, Software Architecture, Coupa Supplier Portal, Web Application Security, Data Streaming, TypeScript, Management of Software Versions, Web Content Accessibility Guidelines, Web Applications, Web Application Frameworks, Web Performance Optimization, ReactJS, Backend, Front End Software Development, Iframes - **Published:** September 13, 2026 - **Apply:** https://www.indeed.com/viewjob?jk=e8b14e728b630f8d ## About the Role * Proven track record as a Frontend Engineer building sophisticated, high-performance web applications, ideally including both complex application interfaces and software embedded into third-party environments. * Deep knowledge of JavaScript/TypeScript, HTML, CSS, the DOM, browser APIs, and the fundamentals of how modern web applications behave and perform - beyond expertise in any individual framework or library. * Strong experience with modern frontend frameworks, preferably React, together with sound understanding of component architecture, application state, data fetching, frontend performance, and modern build and delivery practices. * Experience building performant, data-intensive user interfaces and visualisations, with a strong understanding of how to present and interact with large datasets without compromising responsiveness or usability. * Exceptional attention to detail and a strong sense of visual craftsmanship, with a track record of translating designs into polished, pixel-accurate, responsive, and accessible interfaces. * Strong understanding of browser and web security fundamentals, including cross-origin behaviour, iframes, CSP, CORS, and secure handling of sensitive data, together with a commitment to building accessible experiences to WCAG standards. * Strong software-engineering judgement and problem-solving skills, with the ability to understand backend architecture, APIs and data flows, make pragmatic technical trade-offs, and quickly learn unfamiliar technologies and domains., * Experience building framework-agnostic SDKs, hosted fields, checkout components, or other software designed to run reliably within third-party websites and applications. * Experience with Backend-for-Frontend patterns and server-side technologies such as Node.js, or deeper experience working across frontend and backend architecture. * Experience in payments, fintech, or e-commerce, particularly with PCI DSS, payment forms, security-sensitive customer journeys, or other high-scale transactional environments. ## Description APEXX is pioneering payment orchestration, transforming the global payments landscape with cutting-edge technology and innovation. As a leader in Fintech, we're committed to excellence, driving forward-thinking solutions that empower businesses worldwide., We're looking for a Frontend Engineer to build and evolve the customer-facing surfaces of our payments platform. Your work will span lightweight, embeddable JavaScript SDKs and payment components used within merchant checkout experiences, as well as sophisticated web applications that enable enterprise customers to understand, configure, and manage their payments. This is a hands-on engineering role combining deep frontend expertise with exceptional attention to performance, accessibility, and visual craftsmanship. You'll solve demanding engineering challenges ranging from lightweight, resilient checkout components to rich, data-intensive applications that need to remain fast, intuitive, and responsive while working with complex payment data at scale. Payments are critical, security-sensitive customer journeys, and the software you build needs to perform reliably and precisely across browsers, devices, and assistive technologies. Whether you're building an embedded checkout component or a complex dashboard, we expect the same high standard of engineering quality and user experience. WHAT YOU'LL DO: * Design, build, and maintain robust, lightweight, high-performance JavaScript/TypeScript SDKs and payment components that integrate seamlessly into diverse merchant environments, with rigorous attention to isolation, backwards compatibility, browser behaviour, security, accessibility, and performance. * Build and evolve sophisticated merchant- and internal-facing web applications, creating polished, responsive, and highly performant experiences across complex workflows, large datasets, dashboards, and data visualisations. * Raise the bar for frontend engineering and visual craftsmanship, translating product and design intent into precise, accessible, and intuitive experiences that perform consistently across browsers, devices, and merchant environments. * Work confidently across the frontend/backend boundary, understanding underlying services, APIs, and data flows and, where appropriate, designing and building Backend-for-Frontend services to create performant and maintainable frontend experiences. * Engineer for quality throughout the delivery lifecycle, using appropriate automated testing, performance optimisation, observability, and debugging practices to build reliable software and resolve complex production issues. * Version, document, and publish client libraries with strong semantic-versioning and backwards-compatibility discipline, and contribute to clear integration guidance that enables merchants to adopt and integrate APEXX capabilities successfully. * Collaborate closely with Product, Design, and Engineering to shape well-architected solutions, challenge assumptions, make sound technical trade-offs, and continuously evolve our frontend architecture, engineering practices, and technology choices. ## Related Videos - [Microfrontends at Scale](https://www.wearedevelopers.com/videos/236-microfrontends-at-scale) - [The Resilience of the World Wide Web](https://www.wearedevelopers.com/videos/1281-the-resilience-of-the-world-wide-web) - [Developing the Backend with Stefan Lingler, CTO at Shpock](https://www.wearedevelopers.com/videos/100360-developing-the-backend-with-stefan-lingler-cto-at-shpock) - [Web-Fragments: incremental micro-frontends migration approach for enterprise](https://www.wearedevelopers.com/videos/1587-web-fragments-incremental-micro-frontends-migration-approach-for-enterprise) - [Meet Your New BFF: Backend to Frontend without the Duct Tape](https://www.wearedevelopers.com/videos/682-meet-your-new-bff-backend-to-frontend-without-the-duct-tape) - [Nest.js - TypeScript in the backend can also be clean](https://www.wearedevelopers.com/videos/1033-nest-js-typescript-in-the-backend-can-also-be-clean) ## Related Articles - [What’s the Difference Between Frontend and Backend Development?](https://www.wearedevelopers.com/magazine/240-what-s-the-difference-between-frontend-and-backend-development) - [The Best 7 Frontend Frameworks for Developers in 2025](https://www.wearedevelopers.com/magazine/400-the-best-7-frontend-frameworks-for-developers-in-2025) - [Fully Remote Software Engineer Jobs](https://www.wearedevelopers.com/magazine/447-fully-remote-software-engineer-jobs) - [Frontend Developer Salary in Germany [2023]](https://www.wearedevelopers.com/magazine/195-frontend-developer-salary-in-germany-2023) - [Frontend Developer Salary in The UK](https://www.wearedevelopers.com/magazine/233-frontend-developer-salary-in-the-uk) - [React Developer Salary [2023]](https://www.wearedevelopers.com/magazine/198-react-developer-salary-2023)