Exactly. But many of us do have apps that are beyond the capabilities of a single instance.<p>And in this situation the rule of thumb is to do joins in your application layer so you can store different types data (e.g. graph&#x2F;document&#x2F;relational&#x2F;unstructured) in different systems and easily cache where needed.<p>The fact that so many new databases have been created in the last decade suggests that there are a lot of people who do fall into this camp.