This feature was introduced to resolve resource usage conflicts between order management operations on the backend and checkout operations on the storefront in periods of high load, as well as to speed up the order creation process on the last step of checkout.
With this mechanism, order data from the checkout flow is saved into one storage, while order management operations leverage other storage for read operations. Checkout orders asynchronously move to order management orders storage. This isolation means that the load on checkout does not affect responsiveness for order management.