> ​Does the coordinator "cancel" the mutation on the "committed" nodes (and > how)?
No. Those mutations are applied on those nodes. > Is it an heuristic case where two nodes have the data whereas they > shouldn't and we hope that HintedHandoff will replay the mutation ? Yes. But really you should make sure you recover from this error in your client. Hinted handoff might work, but you have no way of knowing if it has taken place so if ALL is important you should retry/resolve the failed query accordingly.
