MMKV vs AsyncStorage: Boosting React Native Storage Performance

Insight

AsyncStorage is the default key‑value store in React Native, but it serializes every read/write to JSON and hits the bridge on each operation, which can become a bottleneck in data‑heavy screens. MMKV, a native key‑value storage library from WeChat, keeps data in a memory‑mapped file and offers zero‑copy reads, making it up to 10× faster for frequent reads and writes. Switching is straightforward and brings noticeable UI smoothness, especially when persisting form state, caching API responses, or handling auth tokens.

Example

import { MMKV } from 'react-native-mmkv';

const storage = new MMKV();

export const setToken = (token: string) => storage.set('authToken', token);
export const getToken = () => storage.getString('authToken');

The same API works synchronously, so you avoid async/await overhead for simple values.

Takeaway

Replace AsyncStorage with MMKV for any frequently accessed key‑value data. The migration is minimal, and the performance gain translates directly into smoother animations and faster screen transitions.