Technology

I think the main difference between fediverse and email WRT cache instances is that if you create a cache instance for email, you're only caching your personal emails. If you create a cache instance for a lemmy community, you're caching every event on the community.

My intuition says there's probably a breakpoint in community size where the cost of federating all events to the users who subscribe to them becomes greater than the cost of individually serving API requests to them on demand. Primarily because you'll be caching a far greater amount of content than you actually consume, unlike with email.

Edit: That said, scaling out async work queues is a heck of a lot easier than scaling out web servers and databases. That fact alone might skew the breakpoint far enough that only communities with millions of subscribers see a flip in the cost equation...