Techniques for authenticating users when an operation requested by a user in one of the systems of a distributed system is redirected to another system of the distributed system. The user is authenticated in the usual way to the one system but is authenticated to the other system for the redirected operation by an authentication proxy in the first system. The fact that the authentication proxy is providing a redirected operation means that the user who requested the operation has been authenticated to the one system. The other system is thus able to authenticate the user for the redirected operation with different authentication information than would otherwise be required. An example of how the techniques are used is a distributed database system where one of the database systems in the distributed system is a cache for another of the database systems.