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Offline-First SDK

Overview

The Offline-First SDK lets applications use feature flags without an internet connection. Flags are cached locally and synced automatically when the connection is restored.

Key features

1. Local caching

Flags are cached on the device for offline access.

Features: Persistent storage (SQLite, SharedPreferences, UserDefaults), automatic caching on load, cache size limits, TTL-based invalidation.

Example:

val manager = FlagentManager(
    baseUrl = "https://flags.example.com/api/v1",
    offlineStorage = SQLiteOfflineStorage(context),
    cachePolicy = CachePolicy(
        ttl = 24.hours,
        maxCacheSize = 10.megabytes
    )
)
val result = manager.evaluate(
    flagKey = "new_payment_flow",
    entityID = "user123",
    entityContext = mapOf("country" to "US")
)

2. Automatic sync

When back online: background sync, incremental updates, conflict resolution, retry logic. Example: SyncPolicy(autoSync = true, syncInterval = 5.minutes, ...).

3. Predictive caching

Preload by usage, by user, background prefetch. Example: PreloadStrategy.INTELLIGENT, preloadFlags, prefetchEnabled.

4. Conflict resolution

Strategies: Server wins (default), Client wins, Merge (custom), Last write wins.

Architecture

Application → Flagent SDK → Cache Manager → Offline Storage → Network sync when online. Flow: start → load from cache → sync if online → update cache → serve from cache.

SDK implementation

Kotlin (Android/JVM): AndroidOfflineStorage, SQLiteOfflineStorage. Swift: iOSOfflineStorage. JavaScript: IndexedDBOfflineStorage.

API

OfflineStorage: save, load, clear, getFlag, updateFlag. FlagentManager: sync, syncInBackground, enableAutoSync, disableAutoSync.

Configuration

CachePolicy (ttl, maxCacheSize, storageLocation, preloadStrategy, preloadFlags, prefetchEnabled). SyncPolicy (autoSync, syncInterval, syncOnAppStart, syncOnNetworkAvailable, conflictResolution, customMerge). Env: FLAGENT_OFFLINE_STORAGE_*, FLAGENT_CACHE_*, FLAGENT_AUTO_SYNC_*.

Use cases

Mobile app offline; PWA with IndexedDB; desktop with local cache.

Roadmap

Phase 1: Persistent storage, local cache, TTL. Phase 2: Auto-sync, background sync, incremental updates. Phase 3: Conflict resolution, predictive caching, compression, encryption.

Related documentation