Is it possible to store data on Photon servers?


I'm currently developing an app where you will be able to host or join lobbies. To do this I want to generate a unique ID for every lobby that you will need to input to connect to that lobby. This is easy enough however, I want to make sure that there are no duplicates of the ID's i.e. I don't want two concurrently running lobbies to get the same ID. For this I need to save all ID's somewhere and to be able to check that the generated ID isn't already used, and generate a new one. This brings me to the question in the title.