Configuring data consistency
Consistency refers to how up-to-date and synchronized a row of Cassandra data is on all of its replicas. Cassandra extends the concept of eventual consistency by offering tunable consistency. For any given read or write operation, the client application decides how consistent the requested data must be.
Tunable consistency for client requests
Consistency levels in Cassandra can be configured to manage availability versus data accuracy. A tutorial in the CQL documentation compares consistency levels using cqlsh tracing. You can configure consistency on a cluster, data center, or individual I/O operation basis. Consistency among participating nodes can be set globally and also controlled on a per-operation basis (for example insert or update) using Cassandra’s drivers and client libraries.
Start-Up Ideas, Tech Code, Use Cases, Thoughts 