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What is Offline-first?

Offline-first is an architectural approach that prioritizes a seamless user experience regardless of network connectivity. PocketSync implements this pattern by allowing your application to work fully offline while automatically managing data synchronization when connectivity is restored.

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How PocketSync handles offline scenarios

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Local-first operations

  1. Immediate Local Updates

    • All database operations are performed locally first
    • Changes are immediately reflected in the UI
    • No waiting for server response

  2. Change queueing

    • Modifications are recorded in local system tables
    • Changes are queued for later synchronization
    • Order of operations is preserved

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Sync process

  1. Connection detection

    • PocketSync monitors network connectivity
    • Automatically initiates sync when online
    • Handles intermittent connections gracefully

  2. Change resolution

    • Local changes are sent to server
    • Server processes and validates changes
    • Conflicts are resolved using defined strategies

  3. Data consistency

    • Version tracking ensures data integrity
    • Changes are applied in correct order
    • System tables maintain sync state

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Implementing offline-first

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Best practices

  1. Data structure

    await db.execute('''
  CREATE TABLE items (
    id TEXT PRIMARY KEY,
    content TEXT,
    created_at INTEGER,
    updated_at INTEGER,
  )
''');

  2. Error handling

    try {
  await db.insert('items', {
    'id': const Uuid().v4(),
    'content': 'New item',
    'created_at': DateTime.now().millisecondsSinceEpoch,
    'updated_at': DateTime.now().millisecondsSinceEpoch,
  });
} catch (e) {
  // Handle error locally
  // Data will sync when connection is restored
}

  3. UI feedback

    StreamBuilder<List<Map<String, dynamic>>>(
  stream: db.watch('SELECT * FROM items'),
  builder: (context, snapshot) {
    return Column(
      children: [
        // Show sync status
        if (!isOnline)
          const Text('Working offline - changes will sync when online'),
        // Display items
        ListView.builder(
          itemCount: snapshot.data?.length ?? 0,
          itemBuilder: (context, index) => ItemWidget(
            item: snapshot.data![index],
          ),
        ),
      ],
    );
  },
)

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Handling edge cases

  1. Long offline periods

    • Changes are preserved indefinitely
    • Sync resumes automatically when online
    • Data integrity is maintained

  2. Conflict scenarios

    • Multiple devices modifying same data
    • Server-side conflict resolution
    • Custom resolution strategies available

  3. Storage limitations

    • Efficient change tracking
    • Periodic cleanup of processed changes
    • Optimized storage usage

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Benefits

  1. Enhanced user experience

    • No interruption in functionality
    • Immediate response to user actions
    • Smooth transition between online/offline

  2. Data reliability

    • No data loss during offline periods
    • Consistent state across devices
    • Robust sync mechanism

  3. Developer friendly

    • Simple integration
    • Automatic sync handling
    • Built-in conflict resolution

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Common patterns

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Optimistic updates

// Immediately update UI and sync later
await db.transaction(() async {
  await db.insert('items', newItem);
  // UI updates immediately
  // Sync happens in background
});

By following these patterns and best practices, you can create robust offline-first applications that provide a seamless user experience regardless of network conditions.

PocketSyncDatabaseSync Engine