> Markdown version of [/jobs/ext/3725699-senior-frontend-engineer-checkout-all-genders](https://www.wearedevelopers.com/jobs/ext/3725699-senior-frontend-engineer-checkout-all-genders). 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).

---

# Senior Frontend Engineer - Checkout (all genders)

- **Company:** About You
- **Location:** Hamburg, Germany
- **Experience:** Expert
- **Contract:** Permanent contract
- **Skills:** Flutter, JavaScript (Programming Language), HTML5, Automation of Tests, Browser Compatibility, Cascading Style Sheets (CSS), Code Review, Responsive Web Design, TypeScript, Web Content Accessibility Guidelines, Web Applications, Web Performance Optimization, Web Usability, Datadog, ReactJS, Backend, Material UI, Front End Software Development, React Redux, React Testing Library, Restful APIs, Es2015
- **Published:** October 14, 2026
- **Apply:** https://startup.jobs/senior-frontend-engineer-checkout-all-genders-about-you-se-co-kg-10434339

## About the Role

* 5+ years of frontend engineering experience with senior-level ownership (including enterprise-level experience or leading complex frontend setups)
 * Mastering modern JavaScript (ES6+) and advanced TypeScript in strict mode
 * Building complex UIs with React 19, Redux Toolkit, and redux-saga, handling asynchronous flows, multi-step funnels, and payment redirects
 * Optimizing Web Performance and Core Web Vitals to ensure fast loading speeds and high conversion rates
 * Crafting semantic HTML5 and scalable CSS architectures using SCSS, BEM, and modern design systems
 * Developing forms-heavy, internationalized UIs using tools like Formik and react-intl in multi-tenant REST API environments
 * Writing automated tests (Jest, React Testing Library) and working within modern CI/CD pipelines
 * Balancing technical excellence with business priorities, making pragmatic trade-offs to deliver value without over-engineering
 * Communicating with transparency and ownership, proactively raising blockers in fluent English, collaborating across disciplines, and adapting in an agile environment

Nice to have

 * Experience building embeddable widgets / web components or other frontends that run inside third-party sites
 * Business smartness: enterprise-level experience, comfortable talking to C-level
 * Flutter skills

## Description

* Architecting and building modular checkout UI components in TypeScript and React, managing state and side effects with Redux Toolkit and redux-saga
 * Developing payment provider integrations (e.g., Klarna, PayPal, Apple Pay), including widget and redirect flows
 * Owning storefront integration contracts for multi-tenant setups, including embeddable web components, host events, and tracking
 * Optimizing Core Web Vitals, loading speeds, and rendering performance to drive conversion rates and elevate user experience
 * Monitoring and resolving production issues across tenant shops using observability tools like Datadog
 * Translating complex checkout requirements into scalable solutions while ensuring WCAG accessibility, responsive design, and cross-browser compatibility
 * Collaborating cross-functionally with Product, UX, Backend, and QA teams in daily agile workflows to ship features like one-page or multi-step checkout flows
 * Driving engineering standards through thorough code reviews, architectural discussions, and technical refactoring initiatives
 * Expanding core platform capabilities (e.g., for the SCAYLE checkout ecosystem) to enable client customization through injectable content