Unlike either monolithic or master-slave designs, Cassandra makes use of an entirely peer-to-peer architecture. All nodes in a Cassandra cluster can accept reads and writes, no matter where the data being written or requested actually belongs in the cluster. Internode communication takes place by means of a gossip protocol, which allows all nodes to quickly receive updates without the need for a master coordinator.
This is a powerful design, as it implies that the system itself is both inherently available and massively scalable. Consider the following diagram:
Note that in contrast to the monolithic and master-slave architectures, ...