The latest version of the Hector Java client has experimental support for a "virtual keyspaces" feature that transparently adds and removes a prefix to all row keys sent between Hector and Cassandra. There's a small write up of it here:
https://github.com/rantav/hector/wiki/Virtual-Keyspaces The idea is to use a "Shared Keyspace, Shared Column Families" variation of the common "Shared Database, Shared Schema" technique for multi-tenancy. Certainly not applicable for all situations, but makes it very simple to implement multi-tenancy in the application tier. Hector can be found at https://github.com/rantav/hector/ Ed
