offlinearchitecturereact-native

Designing Offline-First Mobile Apps at Scale

January 8, 202615 min read

The Offline-First Mindset
Users expect apps to work regardless of network conditions. Here's how to deliver that experience.

Core Principles
1. Local-first data: Write to local storage first, sync later
2. Optimistic updates: Show changes immediately
3. Conflict resolution: Handle sync conflicts gracefully
4. Queue management: Persist pending operations

Architecture Overview
```
┌─────────────┐ ┌─────────────┐ ┌─────────────┐
│ UI │ ←→ │ Local DB │ ←→ │ Sync Layer │ ←→ Server
└─────────────┘ └─────────────┘ └─────────────┘
```

Implementation with WatermelonDB
WatermelonDB provides excellent offline-first capabilities:
```typescript
import { Database } from '@nozbe/watermelondb'
import SQLiteAdapter from '@nozbe/watermelondb/adapters/sqlite'
const adapter = new SQLiteAdapter({
schema,
migrations,
jsi: true, // Enable JSI for better performance
})
const database = new Database({
adapter,
modelClasses: [Task, Project, User],
})
```

Sync Strategies
#

Last-Write-Wins
Simple but can lose data. Use for non-critical updates.
#

Operational Transforms
Complex but preserves all changes. Good for collaborative editing.
#

Custom Merge Functions
Best of both worlds—define per-field merge logic.

Real-World Example: Inbo App
In the Inbo mobile app, we handle 10,000+ records offline with:
- SQLite for structured data
- File system cache for images
- Background sync with exponential backoff
- Conflict UI for manual resolution

Performance Tips
1. Index frequently queried fields
2. Paginate large datasets
3. Lazy-load relations
4. Use transactions for bulk operations