Cubrid: Sharded, Highly available, Open Source, Free RDBMS
cubrid.org
cubrid.org
No cross-server transactions.
I can instead use my userid as my shard-key and just query the shard holding the data for that user which will be way faster.
The question is can middleware really solve the problem of having to re-engineer when you reach the limits of your current stack?
[1] http://opensourcebuzz.technetra.com/2010/06/21/meet-cubrid-o...