react-native-mmkv

Create an instance with createMMKV() and call synchronous methods like storage.set('key', value) and storage.getString('key'). No await is needed because MMKV memory-maps its file and reads and writes in-process.

Create a StateStorage adapter mapping setItem to storage.set, getItem to storage.getString, and removeItem to storage.remove, then pass it to zustand's persist middleware via createJSONStorage. The same adapter pattern works for redux-persist, jotai, and react-query.

V4 replaced new MMKV() with the createMMKV() factory, renamed .delete() to .remove(), replaced the Mode enum with string literals, and requires react-native-nitro-modules as a peer dependency. Existing data files are preserved, so only API calls need updating.

Yes, MMKV supports AES-128 and AES-256 encryption set via the encryptionKey config option or by calling storage.encrypt(key) at runtime. Encryption is not supported on web, and keys are limited to 16 bytes for AES-128 and 32 bytes for AES-256.

Run a one-time batch migration: read all keys with AsyncStorage.getAllKeys and multiGet, write each value into MMKV, remove them from AsyncStorage, then set a completion flag in MMKV so the migration never reruns. Replace await calls with synchronous MMKV getters afterward.

MMKV has no fixed storage limit, but because it memory-maps the entire file, total size should stay under roughly 100 MB to avoid memory warnings and slow writes. For larger datasets, use a database such as react-native-nitro-sqlite or WatermelonDB.