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APEXX Global is a payment orchestration platform serving enterprise merchants worldwide. They're seeking a Frontend Engineer to build and evolve customer-facing surfaces of their payments platform, spanning lightweight JavaScript SDKs and payment components used in merchant checkouts, as well as sophisticated web applications for enterprise customers to manage their payments.
You'll work on demanding engineering challenges including lightweight, resilient checkout components and rich, data-intensive applications that must remain fast, intuitive, and responsive while handling complex payment data at scale. Payments are security-sensitive customer journeys requiring high standards of reliability, performance, and precision across browsers, devices, and assistive technologies.
Key responsibilities include:
- Design, build, and maintain robust, high-performance JavaScript/TypeScript SDKs and payment components with rigorous attention to isolation, backwards compatibility, browser behavior, security, accessibility, and performance
- Build and evolve merchant- and internal-facing web applications with polished, responsive experiences across complex workflows, large datasets, dashboards, and data visualizations
- Raise the bar for frontend engineering and visual craftsmanship, translating product and design intent into precise, accessible, and intuitive experiences
- Work across the frontend/backend boundary, understanding underlying services and APIs, and designing Backend-for-Frontend services where appropriate
- Engineer for quality using automated testing, performance optimization, observability, and debugging practices
- Version, document, and publish client libraries with strong semantic-versioning and backwards-compatibility discipline
- Collaborate with Product, Design, and Engineering to shape well-architected solutions and evolve frontend architecture
The role is initially remote but will transition to hybrid as APEXX expands their regional presence in Lisbon.
REQUIREMENTS:
- 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 fundamentals of how modern web applications behave and perform
- Strong experience with modern frontend frameworks, preferably React, 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 visualizations with strong understanding of presenting and interacting with large datasets without compromising responsiveness
- Exceptional attention to detail and visual craftsmanship with track record of translating designs into polished, pixel-accurate, responsive, and accessible interfaces
- Strong understanding of browser and web security fundamentals including cross-origin behavior, iframes, CSP, CORS, and secure handling of sensitive data; commitment to building accessible experiences to WCAG standards
- Strong software-engineering judgment and problem-solving skills with ability to understand backend architecture, APIs, data flows, make pragmatic technical trade-offs, and quickly learn unfamiliar technologies
GREAT TO HAVE:
- Experience building framework-agnostic SDKs, hosted fields, checkout components, or other software designed to run reliably within third-party websites
- Experience with Backend-for-Frontend patterns and server-side technologies such as Node.js
- Experience in payments, fintech, or e-commerce, particularly with PCI DSS, payment forms, security-sensitive customer journeys, or high-scale transactional environments
