Primary Node -Down - Replication Queue-Not-Success- Any data Loss

When the Client Send the write operation to CouchBase Server , Primary Node successfully written and sent back the response as Success to Client. Primary Node is down before put the write operation into the replication queue , Whether Data losses will happen or not ?

I believe what you’re asking is if you write a document and the node crashes before it is written to disk and before it is sent into the replication queue will there be data loss? Yes. That said, if you’re using persistto or replicateto and you get an acknowledgement on the durability constraint you’re specifying, this will ensure the durability you’re after.