Wait, is it required to mirror the entire Bluesky history? Can't you just store only new messages? Because the storage requirements (4.5TB according to the article) make it almost impossible to self-host.
Is there any public third party BlueSky storage server yet? Last time I tried setting up an account there it only showed the main instance despite all the fuss about decentralization. Or am I grossly misunderstanding how different it is from the fediverse?
As far as I know, there aren't any yet. Even if there were, I personally wouldn't trust them for the same reason I wouldn't use any Mastodon instance besides mastodon.social: if the PDS shuts down abruptly, your account is gone forever.
Bluesky and ATProto are designed specifically to hide the ways in which it's decentralized.