The document discusses how the author's company OpenSky uses both the Doctrine ORM and ODM in their e-commerce application. Actions involving commerce like orders and transactions are stored in MySQL using the ORM, while other data like products, users, and suppliers are stored in MongoDB using the ODM. The author explains how they define entities and documents and blend the two systems by loading the MongoDB product document reference on the ORM order entity using a post-load lifecycle event listener.