The InStorePickupFulfiller receives order fragments and attempts to purchase the items from the inventory. When the OrderFulfillerTools class takes any item in an in-store pickup shipping group it initiates the InStorePickupFulfiller by defining an inStorePickupShippingGroup=InStorePickupFulfiller mapping.

The InStorePickupFulfiller is associated with an InStorePickupModificationHandler, which is responsible for handling some of the order modification logic.