I see in Aura it is mentioned that it is clustered configuration under "Reliability"
Is this true? When we are creating Database it just asks for Database size and no way to know what is the cluster configuration.
The good part about managed services is that you don't have to worry about the cluster configuration, that's managed for you. So Aura exposes to you a reliable graph endpoint (yes they do so by taking advantage of clustering). One of the purposes of the managed service is to free you up from having to think about these sorts of things so that you can focus on your graph application where you can add value.