Designing an app so that it works without a connection: data is stored on the device, actions are queued, and everything synchronises when the network returns.
Field workers, couriers, warehouse staff, and anyone on a metro or in a basement lose connectivity routinely. An app that shows an error instead of working simply does not get used in those conditions.
We decide early which data must be available offline, implement a local store with background sync, and define explicit conflict rules so two edits of the same record resolve predictably instead of silently overwriting.