As application developers using Cassandra, we also have a choice between immediate and eventual consistency. However, we don't implement this decision by selecting a particular machine to read from: when interacting with Cassandra, the particular node we're communicating with is irrelevant because requests are always forwarded to the node or nodes that should handle them.
Instead, Cassandra has a built-in notion of tunable consistency, which allows us to make a decision for each query about what consistency characteristics we want. Specifically, we tune consistency by telling Cassandra what constitutes a successful request.
