System overview

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Global system overview

PocketSync is a distributed system that enables seamless data synchronization across multiple devices while maintaining data consistency and handling offline scenarios.

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System components

1. Client devices

   • Mobile applications
   • Desktop applications

2. PocketSync server

   • Central coordination point
   • Change processing and distribution
   • Conflict resolution

3. Database layer

   • Local SQLite databases on devices
   • Server-side storage for change history

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Data flow

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1. Local changes

When a device makes changes to its local database:

• Changes are captured through SQL triggers
• Each modification is logged with metadata
• Changes are queued for synchronization

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2. Synchronization process

1. Change detection

   • Device identifies new local changes
   • Changes are packaged with version information

2. Server communication

   • Device sends changes to server
   • Server validates incoming changes
   • Changes are processed and stored

3. Change distribution

   • Server notifies other devices
   • Changes are propagated to online devices
   • Offline devices queue for later sync

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3. Conflict handling

• Server detects conflicting changes
• Applies configured resolution strategy
• Notifies devices of resolution results

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Offline support

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1. Offline operation

• Devices continue normal operation offline
• All changes are logged locally
• Version tracking maintains consistency

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2. Reconnection process

1. State recovery

   • Device reports last sync state
   • Server identifies missed changes

2. Change reconciliation

   • Missed changes are downloaded
   • Local changes are uploaded
   • Conflicts are resolved

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Real-time updates

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1. Change notifications

• WebSocket connections for active devices
• Immediate change propagation
• Efficient delta updates

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2. State management

• Devices maintain local state
• Server tracks global state
• Version vectors ensure consistency

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System guarantees

1. Data consistency

   • Eventually consistent across devices
   • Transactional integrity
   • Conflict resolution

2. Reliability

   • Fault tolerance
   • Data durability
   • Recovery mechanisms

3. Performance

   • Efficient change tracking
   • Optimized sync protocol
   • Minimal network usage