Context: How does an order saving work?
Details: How does \Magento\Sales\Model\ResourceModel\EntityAbstract::_afterSave() work?
Details: How does \Magento\Framework\Model\ResourceModel\Db\VersionControl\Snapshot::registerSnapshot() work?
How does \Magento\Framework\Model\AbstractModel::afterSave() work?

Details: How does \Magento\Sales\Model\ResourceModel\Order\Relation::processRelation() work?