Demo project: React Native mobile app with a Node.js API

This demo project illustrates our approach to cross-platform mobile development. It does not come from a client engagement: it is an application we maintain to show, on a concrete case, the technical choices we recommend.

The modelled case is an application for field teams (technicians, delivery drivers, surveyors) who receive jobs, fill in reports with photos and must be able to work in areas without network coverage.

The app is published on iOS and Android from a single code base, and a Node.js API centralises data and notifications.

Field applications often fail on three points: they do not work without a network, they lose entries when synchronisation conflicts occur, and every fix requires going back through the app stores.

Local storage, synchronisation and the update strategy therefore need to be designed from the start rather than bolted on afterwards.

The app is built in React Native with Expo and TypeScript; navigation, camera and geolocation access go through Expo modules.

A local SQLite database stores jobs and reports; a synchronisation queue records changes made offline and replays them to the API.

The Node.js API (Fastify) exposes REST endpoints with token authentication; PostgreSQL, accessed through Prisma, stores the data with a version number on every record for conflict detection.

Push notifications are sent through the Expo notification service, triggered by the API when a job is created or modified.

EAS Build produces the iOS and Android binaries in the cloud, and EAS Update delivers JavaScript code updates directly to devices (OTA).

The app's data layer is designed around offline mode: all reads come from SQLite, and all writes are first recorded there with a locally generated identifier. A synchronisation module then sends the changes to the API, in order, with retries on failure.

Conflicts are detected on the API side thanks to the version carried by every record. The default rule keeps the most recent change, but some fields (a job's status, for example) apply explicit business rules, and unresolved conflicts are reported to the user.

Push notifications are used to signal an event and trigger a background synchronisation; they never carry sensitive data. Device tokens are managed by the API and invalidated at logout.

Builds are produced by EAS Build with separate profiles (development, staging, production) and OTA updates are published per channel, which makes it possible to test a fix on staging devices before rolling it out to everyone.