Free and open-source database management system
Apache Cassandra is a free and open-source, distributed, wide-column store, NoSQL, database management system designed to handle large amounts of data across multiple commodity servers, providing availability with no single point of failure. Cassandra supports clusters and spanning of multiple data centers[2] with asynchronous and master-less replication. It allows low latency operations for all clients. Cassandra implements a combination of Amazon's Dynamo distributed storage and replication techniques combined with Google's Bigtable data and storage engine model.[3]