Cassandra, in classical literature, was cursed by the god Apollo prophesy truth that would never be believed. Larry Ellison of Oracle may not want to listen to Cassandra either,
NoSQL has interviewed Ryan King, in charge of Cassandra projects at Twitter. King says in the interview that it has a system using mysql+memcache but it become expensive to operate because of the number of people required to maintain it.
Twitter has already evaluated a number of alternatives including Hbase, Cassandra, MemcacheDB and others. It applied a number of criteria to the different systems it was evaluating, and, said King, only Cassandra would fit what it wanted.
After a while, Cassandra will completely replace its current system, once its written some code and turned up the volume on its new features.
So there we have it. MyNoSQL is here.