Beyond the Cloud: Building an Offline

Summary

A digital-first economy assumes constant high-speed internet, leaving mobile wallet apps unusable when connectivity drops, such as on subways or in rural areas. A demo wallet solution combines MongoDB Atlas as the cloud source of truth with ObjectBox as an on-device operational store that mirrors the same schema. The ObjectBox Sync Server continuously bridges the two, enabling local reads and writes that sync automatically when connectivity returns. For offline sends, the wallet checks the requested amount against the last-synced balance to prevent overspending, ensuring safe local operations. The architecture treats connectivity as an enhancement rather than a requirement, keeping the wallet responsive in airplane mode with full data access.

Takeaways

1. 1

   ObjectBox runs natively on the device with the same schema as MongoDB Atlas, so every screen and piece of data works identically whether served locally or from the cloud.

2. 2

   Before any send, the wallet checks the requested amount against the last-synced balance and blocks the send if funds are insufficient, preventing overspending while offline.

3. 3

   MongoDB Atlas hybrid search combines full-text keyword and semantic vector search in a single $rankFusion stage; on-device ObjectBox falls back to HNSW vector search when offline.

FAQ