When your instance needs to fetch from another instance it will
Meaning it will only fetch what is being actively looked at?
Only communities that your users subscribe to will be updated by their “origin” instances.
So when an external community is subscribed to from an account located on your located instance, from the point of subscribing forward, your local instance will begin downloading every single post that will ever be made to that subscribed communty, regardless of who posted it?
Or better yet, do you only store what the users on that instance do (i.e. their posts, and posts to the communities hosted on that instance)?
This does happen, but it also stores what your users do on remote instances as well as “copies” of what they interact with. Images (currently the only media hosted by lemmy servers) are linked to thier “origin” as well. So you are storing text of posts and comments.
This is the main point of confusion to me. From my current understanding, it feels as if it contradicts what you had previously said:
Only communities that your users subscribe to will be updated by their “origin” instances.
If it’s already pulling in all posts and comments on that community, what use is specifically storing anything that the users do on that community? Would it not be already stored?