this post was submitted on 15 Jun 2023
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Lemmy
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Yeah it's cached but it has to offload that at some point right? It'd be crazy for a server to keep a 1:1 copy of every instance and action ever on the fediverse? I'm sure yeah it pools all that info to send back to the other servers but both servers keeping a perfect copy of the information doesn't sound right. I imagine the cache is limited copy of everything and once stuff is sync'd the offload aspects unrelated to their own instance.
Reading the docs now, they don't make it super clear what's cached entirely outside 20 posts when a community is first discovered.
This would also mean any instance that defederates would loose all post/comment/vote history from anyone that wasn't in their local instance. Beehaw currently still has all that from the 2 instances they just defederated from despite no longer being in the pool.
This is why outside of complete madlads intentionally subscribing to everything, instances only pull in communities that at least one user on the instance have subscribed to
The cache still lives on even after blocking, outside of direct admin intervention. Beehaw.org still has everything from users on sh.itjust.works and lemmy.world up till the block, and now the cache is stale.
EDIT: Just tried going to lemmy.directory. Unsurprisingly, their server crashed xD
This seems like a potential severe issue though - with just a few accounts, you could, without arousing too much suspicion, just try to get as much communities mirrored to your server as possible. This also means that, with a sufficient amount of users, every (large) fediverse server will have basically a complete copy of all other servers. It seems to me that this will lead to severe scaling issues, as the cost of hosting an instance will just go through the roof once a certain user count is reached.
The overhead of community mirroring is much lighter than you might imagine. Most of it is just text. An entire community is usually as light as a few kilobytes, especially when you consider that images are not copied over, they are image links pointing to the original instance.
Fair point - thanks for the info!