The industrial pattern of designing databases?

Question

hi,
Assume i have a Geographically (within the same continent) centeralized databased, in each district there are a few outlets and each outlet is a cluster and has it's own database. each outlet sychronizes the database with the Master database that is postiioned in the capital city.
Assume the outlet sells items... each time the customer buys an item, item count in the stock in the current outlet must decrease and also the items sold in the Master database should increase. In an industrial eviorenment what cuases this synchronization of Item count in both databases?
TY