Storing Data on the Device
AsyncStorage, MMKV, SecureStore and SQLite, where each kind of data goes on the device, tokens in Keychain / Keystore, persisting app state
Offline Support
NetInfo and expo-network, isConnected vs isInternetReachable, cached reads, queued writes, offline-first, TanStack Query onlineManager and focusManager, conflicts and idempotent requests
Authentication in React Native
OAuth and OIDC in the system browser, expo-auth-session and react-native-app-auth, native Apple and Google sign-in, token lifecycle and refresh, biometric login
Mobile App Security
Threat model of a mobile app, OWASP MASVS and Mobile Top 10, what the bundle reveals, HTTPS and SSL pinning, root detection vs attestation, sensitive data on screen and in logs, WebView