Building Offline-First Mobile Apps for Factory Floors: Architecture Guide

Why Offline-First Matters for Factories

A production app that shows a spinner and fails when Wi-Fi drops is useless on a factory floor. Operators need to log production counts, scan barcodes, and raise alerts — with or without network. The app must store data locally, continue working, and sync when connectivity returns.

Local Storage Options

SQLite (via react-native-sqlite-storage or sqflite in Flutter) is the most reliable option for structured data. WatermelonDB is excellent for React Native apps with complex relational data and built-in sync support. For simple key-value storage, MMKV is significantly faster than AsyncStorage.

Sync Architecture

Two patterns work for factory apps. Push-on-connect: app stores all actions locally as a queue. When online, the queue flushes to the server in order. Simple, reliable, works for most production logging. Conflict-free replicated data types (CRDTs): for collaborative data where two devices might modify the same record simultaneously. More complex, but eliminates merge conflicts. For most factory apps, the push-on-connect queue is sufficient.

Handling Conflicts

Define which side wins when a conflict occurs. For production counts logged by a single operator, last-write-wins is fine. For inventory quantities that multiple people update, you need a merge strategy. Design your data model to minimise conflicts — e.g., one operator owns one machine's data for a shift.

Testing Offline Behaviour

In React Native, use NetInfo to monitor connectivity. In development, use Charles Proxy or the device network throttling tools to simulate poor/no connectivity. Write automated tests that put the app offline, perform operations, restore connectivity, and verify the server received all data in the correct order.