The Magento system is highly scalable and includes the ability to use multiple databases at the same time, this feature is called a split database solution. This feature is only available in Magento commerce or now also known as Adobe commerce solutions.
Controllers are the most important thing in MVC pattern, controller helps to receive request, process and render pages. To create a frontend controller and to process the request we need to extend our controller class with Magento\Framework\App\Action\Action class this class context gives some added features to handle request type and to validate authorized users and so on. But in this process Magento needs to include so many classes which ultimately increase execution time.