Receiving and processing user orders may include receiving an order for an order quantity of a product from a user computing device, retrieving a threshold inventory quantity of the product, retrieving a last known inventory quantity of the product, comparing the threshold inventory quantity with the difference between the last known inventory quantity and the order quantity, performing an asynchronous reservation of the quantity of the product when the threshold inventory quantity is less than the difference between the last known inventory quantity and the order quantity, and performing a synchronous reservation of the quantity of the product when the threshold inventory quantity is greater than the difference between the last known inventory quantity and the order quantity.