The selling stock level is checked at every interaction with the customer to ensure they get what they expect. SKU stock is allocated per basket while the customer is actively shopping. The stock is unallocated after their basket expires.
When a customer begins shopping again, the stock allocation is restarted and the customer is notified of any changes to their basket. In many instances, there is no effect on the customer’s basket but it does protect against overselling products when the stock is sold out.
Best Before dates are a key property to manage as they significantly affect customer expectations and value perception.