"""In what way is storing your users in different databases by username any better than calling your disk drives by letter?""" Probably the fact that those dri

"""In what way is storing your users in different databases by username any better than calling your disk drives by letter?""" Probably the fact that those drives are local while sharded databases are physically seperate (clusters) of independent machines? Some apps totally suck at this model. Others are perfectly suited. I doubt Twitter needs complex joins, so it should be easy to partition their data. S.