Building Offline-First Mobile Apps with Expo

Mobile apps live in unreliable network environments. Here's how I build apps that work regardless of connectivity.

The Core Pattern

Every data operation goes through a local-first pipeline:

async function saveTransaction(tx: Transaction) {
  await localDB.transactions.insert(tx);
  await syncQueue.push({
    type: 'CREATE',
    table: 'transactions',
    data: tx,
    timestamp: Date.now()
  });
  if (navigator.onLine) {
    syncManager.flush();
  }
}

"Users don't care about your server's uptime. They care that the app works when they open it."

Conflict Resolution

For my finance tracker Koin, I use timestamp-based last-write-wins. It's simple and works for 99% of cases. For the remaining 1%, I show a merge dialog.