During rebalance, WARNING level errors such as
WARN com.couchbase.client.CouchbaseConnection: Reschedule read op due to NOT_MY_VBUCKET error: Cmd: 0 Opaque: 460 Key: membase-test-key-24
can come up. These are safe to ignore, as long as they're small in number and do not persist for a long period of time.
This needs to be documented somewhere in the manuals.