Apache Cassandra is a second-generation distributed database originally open-sourced by Facebook. Its write-optimized shared-nothing architecture results in excellent performance and scalability. The Cassandra storage cluster and S3 archival layer are designed to expand horizontally to any arbitrary size with linear cost.Cassandra’s memory footprint is more dependent on the number of column families than on the size of the data set. Cassandra scales pretty well horizontally for storage and IO, but not for memory footprint, which is tied to your schema and your cache settings regardless of the size of your cluster. some of the important link about casandara is available-here.
