This makes sense but doesn’t this imply that displaying comments under a post is a very expensive operation?
Also not totally clear to me (apologies if I missed it in the post) is where repositories live, I have a bsky account with my own domain, but I am not running anything to host a repo. Am I correct in assuming that bsky is hosting my repo, but I would have the option to self host or move it elsewhere and continue using bsky?
> doesn’t this imply that displaying comments under a post is a very expensive operation?
It would be expensive if you don’t do your own aggregation. The recommendation for social atproto apps is to aggregate the records you care about into a local database and essentially build your app-specific index/cache of the network.
Ctrl+F to this part: “Coincidentally, that’s the exact mechanism you would use for aggregation. You listen to events from all of your app users’ repositories, write them to a local database, and query that database as much as you like with zero extra latency.”.
(One interesting consequence is that indexing the network can also be done by someone on your behalf, see https://slices.network/ for an upcoming experiment in that area.)
> Also not totally clear to me (apologies if I missed it in the post) is where repositories live, I have a bsky account with my own domain, but I am not running anything to host a repo.
Yeah, Ctrl+F here: ”Note that https://alice.com and at://alice.com do not need to resolve to the same server. This is intentional so that having a nice handle like @alice.com doesn’t force Alice to host her own data, to mess with her website, or even to have a site at all. If she owns alice.com, she can point at://alice.com at any server.”
You can inspect where at:// points for your handle in an online browser like http://pdsls.dev. If you put your handle there you’ll see the physical server it resolves to at the top.
Displaying comments is cheap because the AppView (the "cache" layer that consumes the aggregated feed of records from the relay) can maintain a relational database of the social web/graph.
When it receives a post, it creates a row in the Post table. When it receives a comment, it creates a row in the Comment table, which has a column pointing to the Post it's replying to. Then, getting all comments under a post is easy SQL.
About your second question: yes, you're correct. What handle you use and where your data is hosted are completely separate matters.
Also not totally clear to me (apologies if I missed it in the post) is where repositories live, I have a bsky account with my own domain, but I am not running anything to host a repo. Am I correct in assuming that bsky is hosting my repo, but I would have the option to self host or move it elsewhere and continue using bsky?