When systems like mongo-connector tail the oplog, it would be useful to be able to have the cursor tail the watermark reflecting the majority of the cluster, rather than the latest operation in the current nodes oplog. Thus the cursor would only return an oplog entry to the caller once a majority of replicas had processed the oplog entry. This would mean that rollbacks would only need to be handled by the app in the case of catastrophic failures where more than a majority of the cluster was lost rather than on every failover that happens.