It would be great to allow each server to have its own users, which could authenticate only to this particular server. Currently every new connection is authenticated against all backend servers.

I can see many use cases that would benefit from this feature, for example:

Creating a cluster from completely independent db servers

• one or more Maxscale instances as entry points
• every backend server has its own users and databases
• migration of any database (with its own users) between backends
• scallability: more backend servers can be added and populated with existing or new databases

Main advantage is that you can migrate databases between backend servers without changing hostname of the database and connection strings in applications.