In today's mobile app world, users demand fast, responsive, and reliable apps, even when they are offline. Therefore, developers spend tremendous effort on app architectures, supporting offline-first and reactive features, like offline data synchronisation or real-time data and UI updates. However, that was never an easy task.

In early February, the MongoDB team announced the general availability of Realm for Dart and Flutter. Realm is a database designed with the mobile environment in mind - fast, lightweight, and optimised for constraints like computing, memory, bandwidth, and battery usage. With Realm, developers can now create performant, reactive, and offline-first Flutter apps with ease.

In this talk, we will extend the existing Flutter app with reactive features using Realm and will make sure to provide the best possible offline app experience.

Key takeaways:
- The benefits of creating offline-first and reactive apps;
- The advantages of using Realm as a database in Flutter;
- How to add Realm to the new or already existing Flutter app;
- Using Realm for reactive data synchronisation;
- App architecture and design considerations for offline access.