I can't find any docs on this so I assume it's not possible, but...
If you run Sitecore in Azure PaaS and have scale-out enabled (e.g. you're running 2x S3 instances) then can you have a shared/centralized cache, much like the Redis Session State cache?
I'm talking about the built-in
prefetch caches that you can clear from
/sitecore/admin/cache.aspx. Do these have to be stored in-memory on each instance?
If so, it seems a massive performance problem that each time a new instance spins up it will have to re-create all of those caches from scratch when all the other instances have already done the heavy lifting.