Cassandra 2.0 was released a few days ago, and its headline feature is a compare-and-swap operation. Compare-and-swap is not a general transaction facility. At bottom, transactions provide the ability for an application to do multiple operations “together” without interference from other concurrent access to the database. Compare and swap provides a special case of this: the ability to do two operations “together”, one of which is a read from a row (or “partition” in Cassandra), and the other a write to the same row. Being a special case of a transaction is not very exciting in and of itself, because transactions are so general: just about anything is a special case of a transaction.