From my experience I have used proxy servers to refer to different servers (nginx).
I have previously worked on building a mvc framework. Basically there were 8 databases with 10 accounts each. The main database had the server addresses and db credentials for each of the other databases. Whenever a user logged in, the main db will disconnect and connect to the appropriate user database.
I was wondering if there in a more common way to do that other than hard-coding this to the database class(s).
I have been thinking about proxy servers that basically refer a user to servers. So maybe it's possible to do the same but for db servers? (Just a thought..)