ActorDB is ideal as a server side database for apps. Think of running a large mail service, dropbox, evernote, etc. They all require server side storage for user data, but the vast majority of queries is within a specific user. With many users, the server side database can get very large. Using ActorDB you can keep a full relational database for every user and not be forced into painful scaling strategies that require you to throw away everything that makes relational databases good.