One of the most commonly used techniques to integrate different parts of an application has always been to share the same data store, along with the same code base. This is usually known as a monolithic application, and it often ends up with a single data store that hosts the data related to all the concerns within the application.
Consider an e-commerce application. A shared data store would contain all concerns (Example: tables within a relational database) surrounding the catalog, billing, inventory, and so on. There's nothing wrong with this approach per se—for example, in small linear applications where the complexity is not too high. However, within complex Domains, some issues can arise. If you share data across many tables touching multiple application concerns, transactions will have a big impact on performance.
Another less technical problem that could...
