---
name: mobile-offline-storage
description: Cross-platform offline-first data management
version: 1.0.0
category: Data Persistence
slug: offline-storage
status: active
graph:
  domains: [domain:mobile]
  specializations: [specialization:mobile-development]
  skillAreas: [skill-area:mobile-offline-sync, skill-area:mobile-local-databases]
  roles: [role:mobile-engineer]
  workflows: [workflow:feature-development, workflow:release-management]
  topics: [topic:accessibility, topic:offline-first]
---

# Mobile Offline Storage Skill

## Overview

This skill provides cross-platform offline-first data management capabilities. It enables configuration of WatermelonDB, Realm, MMKV, and other offline storage solutions with sync queue architectures.

## Allowed Tools

- `bash` - Execute package managers and build tools
- `read` - Analyze storage configurations and schemas
- `write` - Generate models and sync logic
- `edit` - Update storage implementations
- `glob` - Search for storage files
- `grep` - Search for patterns

## Capabilities

### WatermelonDB (React Native)

1. **Schema Definition**
   - Define table schemas
   - Configure column types
   - Set up relations
   - Handle migrations

2. **Sync Engine**
   - Implement sync adapters
   - Handle conflict resolution
   - Configure batch operations
   - Manage sync state

### Realm (Cross-Platform)

3. **Object Schemas**
   - Define Realm objects
   - Configure primary keys
   - Set up relationships
   - Handle embedded objects

4. **Realm Sync**
   - Configure Device Sync
   - Handle flexible sync
   - Manage subscriptions
   - Handle conflicts

### MMKV

5. **Key-Value Storage**
   - Configure MMKV instances
   - Handle encryption
   - Implement migrations
   - Manage namespaces

### Sync Architecture

6. **Offline-First Patterns**
   - Design sync queues
   - Handle network state
   - Implement retry logic
   - Manage pending operations

7. **Conflict Resolution**
   - Last-write-wins strategy
   - Merge strategies
   - User resolution UI
   - Audit logging

## Target Processes

- `offline-first-architecture.js` - Offline patterns
- `rest-api-integration.js` - API sync
- `graphql-apollo-integration.js` - GraphQL sync

## Dependencies

- WatermelonDB (React Native)
- Realm SDK
- MMKV
- SQLite

## Usage Examples

### WatermelonDB Schema

```typescript
// database/schema.ts
import { appSchema, tableSchema } from '@nozbe/watermelondb';

export const schema = appSchema({
  version: 1,
  tables: [
    tableSchema({
      name: 'posts',
      columns: [
        { name: 'title', type: 'string' },
        { name: 'body', type: 'string' },
        { name: 'is_published', type: 'boolean' },
        { name: 'author_id', type: 'string', isIndexed: true },
        { name: 'created_at', type: 'number' },
        { name: 'updated_at', type: 'number' },
      ],
    }),
    tableSchema({
      name: 'comments',
      columns: [
        { name: 'body', type: 'string' },
        { name: 'post_id', type: 'string', isIndexed: true },
        { name: 'author_id', type: 'string' },
        { name: 'created_at', type: 'number' },
      ],
    }),
  ],
});
```

### WatermelonDB Model

```typescript
// database/models/Post.ts
import { Model, Q } from '@nozbe/watermelondb';
import { field, date, children, relation } from '@nozbe/watermelondb/decorators';

export class Post extends Model {
  static table = 'posts';

  static associations = {
    comments: { type: 'has_many', foreignKey: 'post_id' },
    author: { type: 'belongs_to', key: 'author_id' },
  };

  @field('title') title!: string;
  @field('body') body!: string;
  @field('is_published') isPublished!: boolean;
  @field('author_id') authorId!: string;
  @date('created_at') createdAt!: Date;
  @date('updated_at') updatedAt!: Date;

  @children('comments') comments!: Query<Comment>;
  @relation('users', 'author_id') author!: Relation<User>;
}
```

### Sync Queue Implementation

```typescript
// sync/SyncQueue.ts
interface SyncOperation {
  id: string;
  type: 'create' | 'update' | 'delete';
  entity: string;
  payload: any;
  timestamp: number;
  retryCount: number;
}

class SyncQueue {
  private queue: SyncOperation[] = [];
  private isProcessing = false;

  async enqueue(operation: Omit<SyncOperation, 'id' | 'timestamp' | 'retryCount'>) {
    const op: SyncOperation = {
      ...operation,
      id: uuid(),
      timestamp: Date.now(),
      retryCount: 0,
    };
    this.queue.push(op);
    await this.persistQueue();
    this.processQueue();
  }

  private async processQueue() {
    if (this.isProcessing || this.queue.length === 0) return;

    const isOnline = await NetInfo.fetch().then(state => state.isConnected);
    if (!isOnline) return;

    this.isProcessing = true;

    while (this.queue.length > 0) {
      const operation = this.queue[0];
      try {
        await this.executeOperation(operation);
        this.queue.shift();
        await this.persistQueue();
      } catch (error) {
        operation.retryCount++;
        if (operation.retryCount >= 3) {
          this.queue.shift();
          await this.logFailedOperation(operation, error);
        }
        break;
      }
    }

    this.isProcessing = false;
  }

  private async executeOperation(operation: SyncOperation) {
    switch (operation.type) {
      case 'create':
        return api.post(`/${operation.entity}`, operation.payload);
      case 'update':
        return api.put(`/${operation.entity}/${operation.payload.id}`, operation.payload);
      case 'delete':
        return api.delete(`/${operation.entity}/${operation.payload.id}`);
    }
  }
}
```

## Quality Gates

- Data integrity verified on sync
- Conflict resolution tested
- Offline functionality verified
- Migration tests passing

## Related Skills

- `ios-persistence` - iOS Core Data
- `android-room` - Android Room
- `graphql-mobile` - GraphQL offline

## Version History

- 1.0.0 - Initial release


---
Source attribution: a5c-ai
Original project: https://github.com/a5c-ai/babysitter
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Mega AI Hub.

## Upstream license notice

MIT License

Copyright (c) 2026 Gabriel Moreira

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Mega AI Hub resource metadata

Creator / publisher: a5c-ai
Original project: https://github.com/a5c-ai/babysitter
Attribution basis: Upstream repository explicitly recorded in package mirror path

Fields of work: Development & Engineering
Roles: Backend Developer, Data Engineer, Mobile Developer
Specialties: Backend, Database, Mobile
Tools: Mmkv, Realm, Watermelondb, SQLite
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: a9bf7df1751006b1c256da72729b5710bd7024a64448ac66cda42db0d331f9b7