A Cassandra query is returning stale data even after a successful write. What could be wrong?

Consistency level mismatch: 1) Write with ONE (1 replica) but read with ONE from a different replica that hasn't synced. Fix: use LOCAL_QUORUM for both reads and writes (W+R > RF ensures overlap). 2) Replication lag: recently added node not fully synced. Fix: nodetool repair on the new node. 3) Hinted handoff not delivered: node was down during write, hint stored but not yet delivered. Fix: check