For a project I’m looking for a solution for the following problem:

A user can now login to our ASP.Net musicApp with his/her browser.
Now we want to make it possible to login to the musicstore on devices (smartphone etc.)

The problem is in the fact that we want the possibility that a user can login on his account simultaneously with different devices. Think of using the app with his pc and mobile at the same time. And we don’t want to use Cache if possible.

Now have I learned about Design Patterns, only do not know how to use it in this problem.
Who can help?