Coming up in Cassandra 1.1: Row Level Isolation

Apache Cassandra provides row-level atomicity of batch mutations, ensuring that multiple batched writes to the same row are applied by nodes atomically. However, prior to version 1.1, isolation of such updates was not guaranteed. In version 1.1 and later, row-level updates are made in isolation, guaranteeing that if you update both login and password for a user in the same update, no concurrent read may see only a partial update. These atomicity and isolation guarantees apply to columns written under the same physical row within the same column family and share the same partition key. For atomicity, the guarantee extends across column families (within the same keyspace). However, updates to different column families are not isolated. Internally, row-level atomicity is guaranteed mainly by the commit log and memtable structure of Cassandra's storage engine.