I've been on Lemmy for some time now and it's time for me to finally understand how Federation works. I have general idea and I have accounts on three federated instances, but I need some details.

Let Alpha, Beta, Gamma and Delta be four federated instances. I have an account on Alpha and create a post in a community on Beta. A persoson from Gamma comments on it and a person from Delta upvotes the post and the comment.

The question: On which instances are the post, the comment and the upvotes stored?

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[–] Valmond@lemmy.mindoki.com 9 points 1 year ago (2 children)

Also, all data isn't stored on every Lemmy I stance, only (or mostly I guess) where it is relevant.

[–] ShittyKopper@lemmy.blahaj.zone 13 points 1 year ago (1 children)

As long as 1 person from an instance is subscribed to a community, that person's instance will fetch everything that happens inside that community (and keep storing it even if they later unsubscribe, unless manually purged by an instance admin)

[–] Valmond@lemmy.mindoki.com 8 points 1 year ago

So not everything everywhere but quite not that efficient ...

Thanks for the explanation.

[–] Rottcodd@kbin.social 2 points 1 year ago (1 children)

Right, which on a side note is most of why I have accounts on a number of different instances and regularly switch between them - because each instance is at least subtly different, since they each have different userbases, and thus somewhat different sets of subscribed and thus federated communities.

[–] nils@feddit.de 2 points 1 year ago (1 children)

But if you on instance.alpha subscribe to a community on instance.beta that would federate the community to your local instance, right? Is there something I'm missing?

[–] Rottcodd@kbin.social 2 points 1 year ago

Right, but of course if you don't subscribe to it (and nobody else does) then it doesn't.

So, for instance, if you go in through an account on a narrowly specialized instance, you're potentially not going to see a lot of the communities from other instances at all, even on their All, just because nobody's bothered to subscribe to them. And you'll likely see highly specialized communities that fit well with that instance that you might not see anywhere else.

The smaller the instance is, the more likely that is.

I have accounts on a couple of small instances on which I haven't even bothered to subscribe to anything, since their All already matches what I want frim the instsnce.