yes, that makes sense and I did think about that.
When using GetNextServer how would eureka know that you want a preferred server or a failback?

Then if you're using Application.instances its just a list of all available servers in a random order, you wouldn't be able to tell it to use a preferred server.    

should it be something like
```
public InstanceInfo GetNextServer(bool usePreferred)?

but then how would you know you've used all your preferred instances and should start using the fail-back instances