Have not tried it yet - AppEngine works well enough at present. However, AppScale is just an API shim over memcache and a number of different databases such as

Have not tried it yet - AppEngine works well enough at present. However, AppScale is just an API shim over memcache and a number of different databases such as Redis or mysql. I don't see any reason why it should not work just as well as building directly onto those, and the strict limits placed on the AppEngine DS should make it easy to shard mysql instances.