this might be just my wrong assumption on the way you think of it, but it sounds like in your mind you have this picture where the Redis instances behind IDistributedCache are living inside the same box with your app and spins up and down bundled to your app instance.

But actually it doesnt work like that. In simple terms it s like a remote service. You have a Redis instance(or a cluster of them) and each of your app access them when they are up(or when they need). It s not the case they spin up directly attached to your cloud app when your app itself scales. Take a look at how it is pictured in this blog