React Native MMKV
Fastest key-value storage for React Native, based on Tencent's MMKV (memory-mapped key-value) library. 10x faster than AsyncStorage for synchronous reads/writes. MMKV uses memory-mapped files — reads are direct memory access without I/O overhead. Supports string, number, boolean, and buffer storage with encryption. Used by Discord, Shopify, and others needing high-performance local storage.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
AES-128 encryption at rest. Memory-mapped files are OS-protected. No network exposure. Marc Rousavy maintains. Key management is developer responsibility.
⚡ Reliability
Best When
You need fast synchronous local storage in React Native for small key-value data — settings, tokens, cached values — without AsyncStorage's async overhead.
Avoid When
You need complex queries or large file storage — MMKV excels at fast key-value, not relational data or binary blobs.
Use Cases
- • Store agent settings, tokens, and preferences in React Native with synchronous reads — no await required unlike AsyncStorage
- • Cache agent API responses and computed results locally with MMKV for instant retrieval on next app launch
- • Use MMKV as Zustand persist storage for fast synchronous state hydration on React Native app startup
- • Store agent session state that must survive app restarts with MMKV's persistent memory-mapped storage
- • Use MMKV's encryption support for storing sensitive agent credentials and tokens on-device securely
Not For
- • Large binary data — MMKV is for key-value pairs; use react-native-fs for large files
- • Complex relational data — MMKV is a key-value store; use WatermelonDB or SQLite for relational agent data
- • Android API < 23 — MMKV requires Android API 23+ for full functionality
Interface
Authentication
Local storage — no authentication. Built-in AES-128 encryption for storage contents at rest.
Pricing
Marc Rousavy open source project. MIT license.
Agent Metadata
Known Gotchas
- ⚠ MMKV requires a New Architecture (JSI) or Bridge setup — Expo Go doesn't support MMKV natively; requires a custom dev build with the MMKV native module
- ⚠ MMKV is synchronous — reading on the JS thread is fast but writing large values (large JSON strings) may block the JS thread briefly; keep stored values small
- ⚠ getAllKeys() returns all keys across the MMKV instance — use separate MMKV instances (new MMKV({ id: 'user' })) to namespace agent data and avoid key collision
- ⚠ Encrypted MMKV instances require the same encryption key on every read — if the encryption key changes or is lost (app reinstall), stored data becomes unrecoverable
- ⚠ MMKV doesn't support reactive state out of the box — storage.get('key') is a point-in-time read; use zustand-mmkv-storage or jotai-mmkv for reactive state management
- ⚠ Default MMKV instance shares state across all app components — in multi-user or multi-session agent apps, create isolated instances with unique IDs to prevent cross-session data leakage
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for React Native MMKV.
Scores are editorial opinions as of 2026-03-06.