MMKV Storage Patterns

Quick Guide: Use createMMKV() for synchronous key-value storage (~30x faster than AsyncStorage). One singleton instance per concern (global app, per-user). Use typed hooks (useMMKVString, useMMKVObject) for reactive components. Enable encryption with encryptionKey for sensitive data. V4 is a Nitro Module requiring react-native-nitro-modules and React Native 0.75+.

<critical_requirements>

CRITICAL: Before Using This Skill

All code must follow project conventions in CLAUDE.md (kebab-case, named exports, import ordering, import type, named constants)

(You MUST reuse a single MMKV instance per concern -- NEVER call createMMKV() on every render or in component bodies)

(You MUST use typed getters (getString, getNumber, getBoolean) -- NEVER parse the return value of the wrong getter)

(You MUST use remove() to delete keys -- delete() was renamed in v4 due to C++ keyword conflict)

(You MUST install react-native-nitro-modules alongside react-native-mmkv -- v4 is a Nitro Module)