. https://www.infoworld.com/article/3356758/2-reasons-a-federated-database-isnt-such-a-slam-dunk.html
blog article
It’s often the first problem you solve when moving to the cloud: Your enterprise is using dozens, sometime hundreds, of different heterogenous databases, and now you need to bind them together into hundreds of virtual views of the data in the cloud.What’s good about this is that you don’t need to migrate to new databases, or even move the data from where it’s being currently hosted in the cloud. After all, there may be applications that are dependent on that data, and the last thing you want to do is to store redundant data. So, you federate. That gives you logical centralization of data without having to change where the data is physically stored, cloud or not.But not so fast. There are roadblocks to consider. Here are my top two.First, performance. You can certainly mix data from an object-based database, a relational database, and even unstructured data, using centralized and virtualized metadata-driven view. But your ability to run real-time queries on that data, in a reasonable amount of time, is another story. The dirty little secret about federated database systems (cloud or not) is that unless you’re willing to spend the time it takes to optimize the use of the virtual database, performance issues are likely to pop up that make the use of a federated database, well, useless. By the way, putting the federated database in the cloud won’t help you, even if you add more virtual storage and compute to try to brute-force the performance. DAVID LINTHICUM READ MORE