> the multi-table pipeline write pattern

        WITH new_order AS (
            INSERT INTO order (po_number, bill_to, ship_to)
                 VALUES ('ABCD1234', 42, 64)
              RETURNING order_id
        )
        INSERT INTO order_item (order_id, product_id, quantity)
             SELECT new_order.order_id, vals.product_id, vals.quantity
               FROM (VALUES (10, 1), (11, 5), (12, 3)) AS vals(product_id, quantity)
              CROSS JOIN new_order
        ;

Not super pretty, but it illustrates the point. A single statement that creates an order, gets its autogenerated id (bigint, uuid, whatever), and applies that id to the order items that follow. No network round trip necessary to get the order id before you add the items, which translates into a shorter duration for the transaction to remain open.