It's really their killer advantage. It handles 2 million users, which the nostr network cant come anywhere close to. Nostr needs a big rethink on how to scale to a larger user base.
Bluesky’s PDS server has gotten a lot easier to install…
https://github.com/bluesky-social/pds
It runs on a testnet and not the. Main ‘bluesky’ service which is closed and invite only.
A bluesky PDS is like a relay server. They’ve also got a concept of a GDS which is an indexing server which provides other services, similar to the primal caching relay.
Discussion
They just moved off of a single PDS to multiple which the company controls. A step towards decentralization.