--- title: How Mollie uses Expo to power its multi-platform payments app authors: Vernon de Goede published: August 13, 2025 categories: Users, React Native tags: React Native, monorepo, Expo Modules, React Navigation, OTA Updates, EAS Build, EAS Update --- _This is a guest post from Vernon de Goede - the Director of Engineering and Domain Lead at Mollie where he drives the strategy and execution of the Merchant Experience domain. _ ... ## From a bar in Amsterdam to 250,000+ users In 2019, the story of Mollie and Expo began not in a boardroom, but in a bar in Amsterdam. I met [Cedric van Putten from Expo](https://x.com/cedric_dev) for a few drinks. By the end of the afternoon, I was convinced that Expo was the right platform for Mollie. That same weekend, I built the first version of Mollie’s mobile app using Expo. Six years later, the results speak for themselves: a thriving, secure, and resilient mobile app used by tens of thousands of customers every day. ## Why did Mollie choose Expo? At Mollie we needed to build a mobile app that could scale quickly across platforms — and do so with a team that had little to no native mobile experience. Expo offered exactly what we were looking for: - **Speed of delivery**: A small mobile team rapidly delivered a customer-ready mobile app within weeks - especially impressive, considering building mobile capabilities from the ground up. - **Stability**: Mollie's Expo-powered app is now more resilient than many native counterparts — bug fixes can be deployed instantly without needing to wait for store reviews. - **Developer experience**: With Expo’s transparent engineering culture and excellent documentation, engineers at Mollie were able to onboard quickly and focus on shipping value. - **Trusted relationship**: Since 2019, Expo has maintained a direct Slack channel with the Mollie team. We understand that we got a bit lucky to have that. At the time Expo gave it to us because they "thought we were cool" but now it's an enterprise feature. ## A unique engineering culture At Mollie, **everyone is a full-stack engineer**. Out of 350 engineers, only about 10 had prior React Native experience. The rest? They don’t even realize they’re using React Native (well, until they read this blog...) — they’re simply building features using a **cross-platform component library** (Mollie UI) that abstracts away the mobile-specific details. The architecture makes this possible: - **A shared monorepo** containing all feature code. - **A core team of 5 engineers** maintaining both mobile and web platforms. - A modern **release process** that reduces the gap between mobile and web deployments. - Feature teams free to focus on business logic, without worrying about mobile-specific tooling or constraints. Over time, some engineers upskilled themselves to build [**custom Expo modules**](https://docs.expo.dev/workflow/customizing/) — enabling advanced features like Apple Tap to Pay, used by tens of thousands daily to send and receive payments. ## Application architecture highlights - **React Navigation** powers all navigation, although engineers work with abstractions defined in the UI library which control how screens and animations are happening. - A **cross-platform API library** that provides seamless requests independent of the platform. - A custom **local authentication library** handles secure actions like transfers and approvals. - **Scalable monorepo** structure that allow us to grow into more apps, with clear ownership of each cross-platform feature. - **API gateway** architecture connects to backend services written in both PHP and Java. - **Advanced security**: heavy use of encryption in every API call, especially for sensitive actions like account money movements, MFA, etc. - **Single commands** to set up local environments of all platforms and for the creation of new features - **Simplified** way to manage data with ReduxJS/toolkit/query. - **Cross sharing code** for two apps (one of them for a terminal) and a web platform. - [**Expo Modules**](https://docs.expo.dev/modules/overview/) enable access to native features like Apple Tap to Pay and a safer rooting & jailbreak detection mechanism. ## Beyond the app: A terminal built with Expo Mollie doesn’t just build apps — we build hardware too. Our [terminal device (Tap)](https://www.mollie.com/tap) runs an Android app also built with Expo. This approach ensures consistency across all our customer touchpoints, from mobile apps to physical terminals. ## What Expo enables for Mollie - **Cross-platform velocity**: A feature can be built once and deployed to iOS, Android, and web with just ~15% additional overhead. Going fully native would increase that to 300% and require hiring specialists. - **Rapid iteration**: Fixes and improvements can be shipped on the fly with [OTA updates](https://docs.expo.dev/versions/latest/sdk/updates/), reducing operational risk and improving the customer experience. - **Engineering alignment**: Expo’s engineering-first philosophy and transparent roadmap align closely with Mollie’s values. - **Scalability**: With [EAS Build](https://docs.expo.dev/build/introduction/) and Expo’s tooling, hundreds of engineers — regardless of mobile expertise — can contribute seamlessly to the app. ## Conclusion Mollie is redefining what’s possible with React Native and Expo. What started as a fast-moving MVP is now a critical product used by tens of thousands to send and receive money securely. With a forward-thinking architecture, empowered engineers, and the right tools, Mollie continues to push the boundaries of what cross-platform apps can achieve.