Realm is designed for fast local data storage on mobile devices. It offers near-native speed with low latency for read and write operations, helping maintain smooth UI animations at 60fps or higher. Realm uses zero-copy architecture, which reduces memory overhead and CPU usage compared to traditional SQLite or JSON storage. This efficiency helps save battery life by minimizing background processing.
To keep your app smooth, avoid blocking the main thread with heavy Realm queries. Use asynchronous Realm APIs to fetch or write data without freezing the UI. Batch writes together instead of many small writes to reduce disk I/O. Also, use Realm's live objects and notifications to update UI reactively, so you only re-render components when data changes, saving CPU cycles.
Adding Realm to a React Native app increases the bundle size by about 5-10MB depending on platform and configuration. This is moderate and usually acceptable for apps needing local database features. Realm's native libraries are loaded on startup, which can add a small delay (under 500ms) to app launch time. To minimize impact, initialize Realm lazily after the splash screen or use code splitting.
Realm uses native libraries on both iOS and Android, but setup differs. On iOS, Realm integrates with Swift/Objective-C runtime and requires CocoaPods or Swift Package Manager. On Android, it uses native JNI bindings and Gradle dependencies. iOS apps require code signing for Realm binaries, while Android apps need proper ABI splits to reduce APK size. Performance is similar, but Android devices vary more in hardware, so test on multiple devices.
Both Apple App Store and Google Play require apps to handle user data securely. Realm stores data locally, so ensure you encrypt sensitive information using Realm's encryption features. Follow platform privacy policies by disclosing data storage in your privacy policy. Also, avoid excessive background data access to comply with battery and performance guidelines. For iOS, Realm binaries must be properly signed to pass App Store review.
Long load times often happen if you perform heavy Realm queries or data migrations on the main thread during screen load. Also, initializing Realm synchronously before UI renders can block the app. To fix this, move Realm initialization and queries to background threads or use async APIs. Avoid large data reads at startup; load data incrementally or on demand.