Denormalization is often a practical answer; the order service keeps an (immutable) copy of the customer's name and delivery address. If the customer changes t

Denormalization is often a practical answer; the order service keeps an (immutable) copy of the customer's name and delivery address. If the customer changes the address, it will only matter for new orders. One can argue that this is actually a sensible behavior, because there's a point after which you can't change the delivery address anyway (once it has been handed over to the delivery service, for example), and this behavior of copying the address just moves the point a bit. Likewise, when a customer buys a product, a copy of the product description and price is included in the order; if the price changes between the checkout and the delivery, it's good if that isn't reflect in the amount that is invoiced. After all, the checkout established a contract that cannot be easily changed retroactively.