Does PieFed vary much from your Lemmy / AT analysis?

For Activitypub, a weakness is that the server has to host all the visible content to the server. So for example if lemmy got really big, and you wanted to host a tiny server but are subscribed to most lemmy comms, your server ends up hosting and fetching a copy of everything posted in these communities, which can add up to A LOT, in terms of network usage, and computational power. (For example see the debacle where an Australian sever (I think aussie.zone) struggled with this and was weeks behind fetching content from lemmy.world since so much content comes from that instance).

This probably would scale pretty terribly if it got anywhere near the size of reddit.

ATProto gives a scalable solution to this (but comes with tradeoffs). Where you can create your own “instance” PDS (Personal Data Server), without hosting all the posts federated to you, since this is hosted by a “relay” which does most of the heavy lifting computationally. So it ends up with a solution that looks more centralised (since there is less incentive to host relays, so fewer relays), but also much more friendly to people who wanna host their own “PDS” and therefore control their data. This is also very helpful with scalability and solves some of the weird federation quirks activitypub has (ie. you can’t see a lemmy community or mastodon account until someone on your instance subscribes or follows it).

Very interesting, thanks.

Atproto scales quadratically, [...] harms performance AP scales horizontally

Clearly true. But this suggests to me that ATProto might still work well with, say, 5 or 15 "PDS"s. That is still enough IMO to guarantee a high level of pluralism.

In a commercial market, let's say for telephony or cars or web browsers, we readily accept that there are only a handful of players. Indeed, there's generally an optimal number, high enough to guarantee competition but low enough that we can keep track of the brands and trust that they won't go out of business tomorrow.

And nothing is stopping at least one of those few brands from being a "good guy", akin to Mozilla's historic role in the web-browser market. It could be run by say, Wikimedia, for example. At least we would know that it would not disappear tomorrow, which is more than can be said for most Lemmy instances.

I agree that there should be enough space for both ATProto and AP to thrive.

I think in order for both to work towards a better fediverse, there needs to be a "true" sync. Not like the bridge Bluesky is maintaining, we need something to sync both ways. Even if its just a subset with just public posts to begin with.

I know a lot of fediverse software has their own API that extends their own functionality beyond the AP protocol, just to make things more complicated :). But it does help with say bookwyrm needs to know something specific from another bookwyrm instance.

Would SSO every be possible with ActivityPub?

Like if you built a new app (network) on AP and allow people to sign in with their Mastodon handle?