I wanted to ask a question regarding data persistence strategies for an MMO. I have some experience in the games industry with social synchronous games. At Zynga, we stored static proto data in XML on both the client and the server and stored instance/runtime data in membase. For clarity sake, proto data for a Potion would be PotionName or MaxCharges, while runtime/instance data would be something like ChargesRemaining. So basically, if a player picks up a potion the instance is (via prediction) created from XML data on the client, the request gets sent to the server where the instance is created from XML and then added to membase.

Is the same strategy that would be used for soemthing like an MMO? Would it be feasible to have static proto data in some kind of in-memory no-sql database on both client and server with instance data being stored on the server in a more enterprise level database? Or should all data (proto/instance) be stored on the server and the client gets everything from server?

I know a lot of this might on certain game requirements, however, i'm basically looking for some general opinion/best practices here if there are any.