Senior Frontend Developer

At VodafoneZiggo, I served as a Senior Frontend Developer on an assignment through Rebels, contributing to the development and optimization of the company's flagship mobile application serving over 3 million active users across the Netherlands. This enterprise-scale React Native application with Expo provides comprehensive account management, real-time usage tracking, billing, and self-service capabilities for VodafoneZiggo customers.

My primary responsibilities involved architecting and implementing new features using React Native with TypeScript, focusing on creating performant, user-friendly interfaces that work seamlessly across both iOS and Android platforms. I built a scalable design system containing 100+ reusable components, each meticulously documented in Storybook to ensure consistency and enable rapid feature development across the development team. This component library reduced development time by 50% and became the foundation for all new feature work.

State management was a critical aspect of the application - I implemented advanced patterns using Redux Toolkit and RTK Query for efficient data fetching and caching. This architecture enabled intelligent sync capabilities for offline-first functionality, ensuring users could access key information even without network connectivity. Push notifications were integrated via Firebase Cloud Messaging, while deep linking enabled seamless navigation from marketing campaigns and customer service communications.

Performance optimization was paramount for an application of this scale. I reduced initial load time by 60% through code splitting, lazy loading, and bundle size optimization techniques. Time to Interactive was improved to under 2 seconds through careful optimization of the rendering pipeline and strategic use of React.memo and useMemo hooks. The application consistently achieves 99.9% uptime SLA and maintains a 4.7-star rating on the App Store and 4.5 on Google Play with 500K+ reviews.

Quality assurance was comprehensive - I maintained 90%+ test coverage using Jest and React Native Testing Library, writing both unit tests for individual components and integration tests for complex user workflows. Accessibility was a core focus, implementing WCAG 2.1 AA compliance throughout the application with semantic markup, screen reader support, and keyboard navigation. Automated accessibility testing via axe-core and manual testing ensured an inclusive experience for all users.

I established robust CI/CD pipelines with automated testing, linting via ESLint with strict TypeScript rules, and code quality monitoring through SonarQube. Working closely with UX designers, backend engineers, product owners, and QA specialists, I participated in agile ceremonies and contributed to technical decision-making. The role significantly enhanced my expertise in enterprise mobile development, accessibility standards, and large-scale React Native architecture.