Background Execution Constraints
Mobile OSes aggressively limit background execution to preserve battery. iOS allows 30 seconds after backgrounding, Android Doze mode restricts background work. Apps must use system-provided APIs for background tasks: BackgroundTasks (iOS), WorkManager (Android). Understanding these constraints is essential for reliable background processing.
iOS Background Modes
Enable background modes in Xcode capabilities: Audio (music playback), Location (GPS tracking), VoIP (calls), Background fetch (periodic updates), Remote notifications (push-triggered tasks), and Background processing (maintenance tasks). Use BGTaskScheduler for iOS 13+ with BGAppRefreshTask for quick updates and BGProcessingTask for longer operations.
iOS terminates apps that abuse background modes - only use what you genuinely need.
Android WorkManager
WorkManager is the recommended solution for deferrable, guaranteed background work. Define Worker classes with doWork method, create WorkRequest with constraints (network, charging, battery), enqueue work with WorkManager, and observe work status with LiveData. WorkManager handles API level differences and respects Doze mode automatically.
Scheduling Strategies
Choose appropriate scheduling: OneTimeWorkRequest for single execution, PeriodicWorkRequest for recurring tasks (minimum 15 minutes), ExpeditedWorkRequest for important work, and chained work for dependencies. Set constraints wisely - requiring WiFi and charging ensures work runs when device is idle.
Battery Optimization
Minimize battery impact by batching network requests, scheduling work during charging, using exponential backoff for retries, avoiding wake locks, and deferring non-critical work. Users uninstall apps that drain battery - optimize aggressively.
Data Sync Patterns
Implement efficient sync: delta sync (only changed data), conflict resolution (last-write-wins or custom), offline queue (retry failed uploads), and sync indicators (show users sync status). Use background tasks for uploading analytics, syncing user data, and downloading content updates.
Testing Background Tasks
Test background execution by simulating background entry, using debug menu to trigger tasks immediately, testing with device in Doze mode, verifying task completion within time limits, and monitoring battery usage. Background bugs are hard to reproduce - test thoroughly.