Field users lose signal in the middle of a task. The app still has to work. Then it has to catch up without losing a record.

We faced this in a real-estate CRM app that handles 100K+ leads a month. The rebuild made it about 30% faster.

Our take

Three places hold the truth:

  • a local store on the phone
  • an outgoing sync queue
  • the server

The UI updates optimistically from the local store. When the network is back, each queued change reconciles or rolls back. The server has the final word.

That works well for one user on one device.

Where it hurts

Two people edit the same record while both are offline.

Both changes reach the server later. One of them has to lose, or the two have to merge.

Options we weighed:

  • last write wins. Simple, but it silently drops someone's work.
  • field-level merge. Fairer, but you need to track changes per field.
  • ask the user. Safest, but it interrupts the flow.

Your turn

Two offline edits collide. Who wins in your app, and how do users find out?