A cloud POS that stops working when the internet drops is a queue of frustrated customers waiting to happen. Offline-first design treats the network as optional.
Local first, sync second
Each terminal writes sales to a local database and a durable outbox. A background sync service pushes changes to the cloud and pulls price and stock updates, resolving conflicts with clear rules — for example, the central price list always wins, while sales are never discarded.
Idempotent APIs
Every sale carries a client-generated ID so the server can safely accept retries. This one decision removes a whole class of duplicate-invoice bugs.
Visibility for owners
When terminals come back online, the owner dashboard updates within seconds, and any terminal that has been offline too long raises an alert.