Abstract: An apparatus includes at least one processor and at least one memory storing instructions that, based on being executed by the at least one processor, perform operations. The operations includes: receiving, from a user terminal, a request for return of inventory information of at least one item stored at a location at a first time point, in response to receiving the request for the inventory information, obtaining event information including pieces of information each corresponding to an event that caused a change in inventory of items associated with the location before the first time point, generating the inventory information of the at least one item stored at the location at the first time point based on the event information, and transmitting the inventory information to the user terminal.