The only information that actually gets federated to other servers is public information that is globally visible anyway. Fediverse servers don’t (or at least SHOULDN’T) trust each other.
It’s not actually that hard to index and store the information, especially if you just want textual post data - Mastodon at least can serve you an easy to parse version of a user’s posts if you request it. Sure you need to poll for the information rather than it just being sent to you, but I think if they were motivated enough they could do it.
The only information that actually gets federated to other servers is public information that is globally visible anyway. Fediverse servers don’t (or at least SHOULDN’T) trust each other.
It’s not actually that hard to index and store the information, especially if you just want textual post data - Mastodon at least can serve you an easy to parse version of a user’s posts if you request it. Sure you need to poll for the information rather than it just being sent to you, but I think if they were motivated enough they could do it.