Lots of traffic, lots of posts, lots of comments, … That’s going to need more storage, more bandwidth, more CPU power, higher running costs. The original instance hosting the community bears a higher load than the instances that duplicate it.

Ideally, there would be a way to more evenly distribute this load across instances according to their resources, but from my (currently limited) knowledge, I don’t think Lemmy/ActivityPub is really geared for that kind of distributed computing, and currently I don’t believe that there’s a way to move subs between instances to offload them (although I believe some people may be working on that).

Perhaps the Lemmy back-end could use a distributed architecture for serving requests and storage, such that anyone could run a backend server to donate resources without necessarily hosting an instance.

For example, I currently have access to a fairly powerful spare server. I’m reluctant to host a Lemmy instance on it as I can’t guarantee its availability in the long term (so any communities/user accounts would be lost when it goes down), but while it’s available I’d happily donate CPU/storage/bandwidth to a Lemmy cloud, if such a thing existed.

There are pros and cons to this approach, but it might be worth considering as Lemmy grows in popularity.