The other subtlety is in being able to prevent the server from servicing requests when it shouldn't be (to avoid consistency issues). What you don't want is a

The other subtlety is in being able to prevent the server from servicing requests when it shouldn't be (to avoid consistency issues). What you don't want is a client not aware of the new configuration -- or reading and writing before the new one is ready. That's where vbucket states allow us to atomically move things. It's not obvious from your doc how one can actually accomplish this with zero downtime while maintaining consistency.