# Data Persistence (React Native)

> AsyncStorage, MMKV, SQLite, Realm, secure storage, caching strategies

- 20 interview questions
- Mid-Level
- [Interview Questions: React Native](https://sharpskill.dev/en/technologies/react-native/interview-questions.md)

## 1. What is the main characteristic of AsyncStorage in React Native?

**Answer**

AsyncStorage is an asynchronous, unencrypted, persistent key-value storage system. It works globally across the app and stores data as strings. It's the simplest storage solution built into React Native, ideal for simple user preferences or non-sensitive data.

## 2. How to store a JavaScript object in AsyncStorage?

**Answer**

AsyncStorage can only store strings. To store a JavaScript object, it must be serialized with JSON.stringify() before storing, then deserialized with JSON.parse() when reading. This step is mandatory because AsyncStorage does not accept objects directly.

## 3. What is the main advantage of MMKV compared to AsyncStorage?

**Answer**

MMKV (Memory-Mapped Key-Value) offers performance up to 30 times faster than AsyncStorage thanks to memory-mapping and synchronous data access. Developed by WeChat to handle billions of users, it's particularly suited for applications requiring frequent reads/writes or large data sizes.

## 17 more questions available

- When should SQLite be used instead of AsyncStorage or MMKV?
- What is the main characteristic of Realm compared to SQLite?

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## Other React Native interview topics

- [JavaScript Essentials](https://sharpskill.dev/en/technologies/react-native/interview-questions/javascript-essentials.md): 25 questions, Junior
- [React Fundamentals](https://sharpskill.dev/en/technologies/react-native/interview-questions/react-fundamentals.md): 20 questions, Junior
- [React Native Basics](https://sharpskill.dev/en/technologies/react-native/interview-questions/react-native-basics.md): 22 questions, Junior
- [React Hooks](https://sharpskill.dev/en/technologies/react-native/interview-questions/react-hooks.md): 20 questions, Junior
- [TypeScript for React & React Native](https://sharpskill.dev/en/technologies/react-native/interview-questions/typescript-for-react-native.md): 22 questions, Junior
- [React Native Components & API](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-components-api.md): 20 questions, Junior
- [React Native Styling & Layout](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-styling-layout.md): 18 questions, Junior
- [React Native Navigation](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-navigation.md): 22 questions, Mid-Level
- [React Native State Management](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-state-management.md): 24 questions, Mid-Level
- [React Native Networking & API](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-networking-api.md): 20 questions, Mid-Level
- [Forms & Validation](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-forms-validation.md): 18 questions, Mid-Level
- [React Native Animations](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-animations.md): 22 questions, Mid-Level
- [Native Modules & Bridge](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-native-modules.md): 20 questions, Mid-Level
- [Platform-Specific Code](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-platform-specific-code.md): 18 questions, Mid-Level
- [Permissions & Device APIs](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-permissions-apis.md): 20 questions, Mid-Level
- [Push Notifications](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-push-notifications.md): 18 questions, Mid-Level
- [React Native Testing](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-testing.md): 20 questions, Mid-Level
- [React Native Debugging](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-debugging.md): 18 questions, Mid-Level
- [Build & Deployment](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-build-deployment.md): 20 questions, Mid-Level
- [Expo vs React Native Bare](https://sharpskill.dev/en/technologies/react-native/interview-questions/expo-vs-bare-rn.md): 18 questions, Mid-Level
- [Performance Optimization](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-performance-optimization.md): 24 questions, Senior
- [Memory Management](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-memory-management.md): 20 questions, Senior
- [Architecture Patterns](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-architecture-patterns.md): 22 questions, Senior
- [React Native New Architecture](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-new-architecture.md): 24 questions, Senior
- [Security Best Practices](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-security-best-practices.md): 20 questions, Senior
- [Offline-First Architecture](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-offline-first.md): 20 questions, Senior
- [React Native CI/CD](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-ci-cd.md): 20 questions, Senior
- [Monorepo & Code Sharing](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-monorepo-architecture.md): 18 questions, Senior
- [Advanced Topics](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-advanced-topics.md): 22 questions, Senior
- [App Lifecycle & Background Execution](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-app-lifecycle-background.md): 20 questions, Mid-Level
- [Authentication & Session Management](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-auth-session-management.md): 22 questions, Mid-Level
- [Monitoring & Crash Reporting](https://sharpskill.dev/en/technologies/react-native/interview-questions/rn-monitoring-crash-reporting.md): 20 questions, Senior

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