What are Cassandra consistency levels and when do you use each?

Consistency level determines how many replicas must respond for a read/write to succeed. Common levels: ONE: one replica acknowledges. Fastest; potential for stale reads. For non-critical reads. QUORUM: majority (RF/2 + 1) of replicas acknowledge. Balances consistency and availability. For most production reads/writes. ALL: all replicas acknowledge. Strongest consistency; any node failure = failur