Mobile — Databases & Storage

Local storage on mobile is mostly SQLite under different wrappers, with key-value stores as the small/fast tier and a handful of object/NoSQL options. For sync engines see PWA and realtime. For server-side databases see databases-orms.

iOS / Swift

• ★ SwiftData — Apple's Core Data successor (iOS 17+). Macros + Core Data backend; CloudKit sync built-in. The default for new SwiftUI apps.
• Core Data — still the longest-running iOS persistence; not deprecated.
• ★ GRDB — best-in-class SQLite library; reactive (ValueObservation); type-safe; excellent docs. MIT.
• SQLite.swift — simpler SQLite wrapper.
• Realm — MongoDB-owned object DB; free SDK; Atlas Sync paid.
• Defaults (sindresorhus) — type-safe UserDefaults wrapper.
• KeychainAccess — Keychain wrapper for secrets.

Android / Kotlin

• ★ Room (Jetpack) — SQLite ORM; the default. Multiplatform support added in Room 2.7.
• ★ DataStore (Jetpack) — replaces SharedPreferences for typed prefs.
• SQLDelight — type-safe SQL across KMP; the default for KMP apps. Apache 2.0.
• Realm Kotlin — KMP-supported.
• ObjectBox — fast NoSQL; free + paid sync.
• MMKV (Tencent) — fast KV; cross-platform; faster than DataStore for hot paths. BSD.

React Native

• ★ op-sqlite — fast SQLite for RN; New-Arch friendly.
• expo-sqlite — Expo's official; great for most.
• react-native-quick-sqlite — older fast bindings; superseded by op-sqlite for many.
• Drizzle + expo-sqlite — typed local DB.
• ★ MMKV (react-native-mmkv) — fast KV; replaces AsyncStorage.
• AsyncStorage — built-in; slow.
• react-native-keychain — secure storage.
• WatermelonDB — local-first reactive DB; sync-able.

Flutter

• ★ Drift — typed SQLite ORM; reactive queries; the recommended default.
• sqflite — bare SQLite plugin; minimal.
• Isar — fast NoSQL; check current maintenance.
• Hive / hive_ce — KV store; hive_ce is the maintained fork.
• shared_preferences — small typed prefs.
• flutter_secure_storage — Keychain / Keystore wrapper.

KMP / Compose Multiplatform

• ★ SQLDelight — multiplatform type-safe SQL.
• Room 2.7+ — KMP-capable.
• Realm Kotlin — KMP.
• multiplatform-settings — small KV across platforms.
• Store5 — caching / repository layer.

Sync engines (local-first)

• WatermelonDB — RN; can sync to your backend.
• PowerSync — Postgres ↔ SQLite sync; iOS / Android / RN / Flutter.
• ElectricSQL — Postgres ↔ SQLite sync.
• Triplit, InstantDB — full sync stacks.
• CouchBase Lite + Sync Gateway — paid + open-source pieces.
• Yjs / Automerge — CRDT-shaped multi-user sync.

Secure / encrypted storage

• ★ iOS Keychain — built-in secure storage; access via Security.framework or wrappers (KeychainAccess).
• ★ Android Keystore — hardware-backed key storage.
• react-native-keychain, expo-secure-store, flutter_secure_storage — wrappers.
• MMKV with encryption — opt-in AES.

File storage

• iOS — FileManager, App Group containers, iCloud Documents.
• Android — Scoped Storage (Android 11+), MediaStore, app-specific folders.
• expo-file-system, react-native-fs, path_provider (Flutter).

Pick this if…

• iOS-only, new app: SwiftData; reach for GRDB if you outgrow it.
• Android-only, new app: Room + DataStore + MMKV for hot paths.
• RN: op-sqlite or expo-sqlite + Drizzle for typed access; MMKV for KV.
• Flutter: Drift + flutter_secure_storage + shared_preferences.
• KMP shared persistence: SQLDelight or Room 2.7.
• Local-first multi-device sync: PowerSync / ElectricSQL or WatermelonDB.
• CRDT collaborative: Yjs or Automerge — link to realtime.