how Cassandra chooses the coordinator node and the replication nodes?

Question

How the Cassandra client chooses the coordinator node? is the coordinator node stores the data sent by the client before replicating?

Answer 1

The coordinator node is typically chosen by an algorithm which takes "network distance" into account. Any node can act as the coordinator, and at first requests will be sent to the nodes which your driver knows about. But once it connects and understands the topology of your cluster, it may change to a "closer" coordinator.

The coordinator only stores data locally (on a write) if it ends up being one of the nodes responsible for the data's token range.