Abstract: Techniques are described for scheduling open orders. Open orders can include back orders and new sales orders. The techniques can reallocate confirmed stock (e.g., stock that is in inventory but been assigned to an existing order) and unconfirmed stock (e.g., stock that is in inventory but has not been assigned to an existing order). An order typically consists of multiple line items where each line item is a request for a quantity of an item of interest. Each line item within an order can be fulfilled when inventory is allocated to the order. In some embodiments, the stock can be allocated to back orders based on a priority that has been assigned to each order. This allows orders of high priority to be processed before orders of low priority. In other embodiments, the techniques can parallel process the allocation of inventory to improve system performance.