you are right, it is used in a subset of cases. However, I think that is better than adding to the command.
The backupResponse is needed because I'm replicating to the backup site concurrently with the local replication (send to backup site, then send to local site and await, finally await reply from backup site). So, I need to "transport" the backupResponse between interceptors...
The other suboptimal alternative would be replicate local (and await sync) and then replicate to backup site (and await sync)