When does product inventory decrease during the ordering process?

The product inventory decreases at the moment the order is actually placed. This is when the system registers a confirmed purchase, which reflects the customer's intent to buy the specified quantity of a product.

During this step, the inventory management system updates to reserve the stock for the buyer, effectively reducing the available inventory for that item. This process ensures that once a customer has committed to purchasing a product, it can't be sold to another customer until the order is either fulfilled or canceled.

Adding a product to the cart does not immediately affect inventory levels, as multiple customers can hold items in their carts without necessarily completing the purchase. Similarly, while the order is being processed, the inventory may still show as available until the order confirmation happens. Payment completion is also not the point of inventory deduction, since payment might not be confirmed yet when inventory changes take place. Thus, placing the order is the critical action that leads to the decrease in inventory levels.