Denormalization is often a practical answer; the order service keeps an (immutable) copy of the customer&#x27;s name and delivery address.<p>If the customer changes the address, it will only matter for new orders.<p>One can argue that this is actually a sensible behavior, because there&#x27;s a point after which you can&#x27;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.<p>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&#x27;s good if that isn&#x27;t reflect in the amount that is invoiced. After all, the checkout established a contract that cannot be easily changed retroactively.