The Cassandra database serves as a “scalable system of record” in the big data world, says Jonathan Ellis, vice president of the Cassandra project. Apache received the project from Facebook, which open-sourced Cassandra in 2008. Whereas Hadoop undertakes data analysis, Cassandra provides a data store for applications, often highly scalable ones on the Web. Netflix, for example, runs many Cassandra clusters, Ellis says.
Cassandra offers fault tolerance on commodity hardware or cloud infrastructure and can be replicated across multiple data centers. Slated for July, Cassandra 2.0 will include support for CAS (compare-and-set) capabilities, to combine read and update into a single operation; trigger support, for defining actions in response to updates made to different tables and further reduction in request latency.