alt Hacker NewsI'm pretty sure the previous poster was not referring to the fact a PDS holds all of YOUR data -- mastodon servers do the very same thing.
I think they might've been referring to the fact that ATProto requires the existence of big, central relay/BGS servers, which are forced to index all the data of everyone on the network for the whole "social" aspect to work well.
That requirement makes hosting a complete, independent ATProto stack much more expensive and resource intensive than hosting an ActivityPub server, thus making ATProto harder to like, actually decentralize. (Correct me if I'm wrong, but I think currently the only independent, full-network relay is the corporate Bluesky one?)
To conflate having doubts about ATProto's design with "not liking fun" feels silly to me; it's a much less battle-tested design, doubts are warranted.
Replies
The "big" central relay servers are not big at all and are actually quiet cheap: https://whtwnd.com/bnewbold.net/3lo7a2a4qxg2l
This submission is about BlackSky doing the whole stack themselves. There are other single node app-views. So, thanks for asking, with apologies, let me correct you: you are wrong.
There are lots and lots of full network relays. A couple that run a full network relay on a < $5/mo VPS . See my other comments in this thread, https://news.ycombinator.com/item?id=47302514
If all you want is like and replies (which is the biggest huge part of the app view responsibility), Constellation has done that, is open source, and can do a full network link indexing on a raspberry pi. And which runs public endpoints you can just use, that many apps rely on.
Atproto unlike Mastodon also faces these challenges that, if you tried to do them on Mastodon, would get you screamed at and banned from instances. Fediverse broadly doesn't want you to use "their" data. You can't write search tools. As a result, Mastodon doesn't need anywhere near the complexity, because these unofficial but vociferously enforced terms-of-service disallow thorough interconnection to begin with. Makes it technically much simpler to pull off! No one is allowed to get a full fire hose. No broad app views are allowed. Dunno if this is still true, but for the longest time you wouldn't get likes or comments from someone unless they were already followed by someone on your fedi, and it's a direct result of this deliberate explicit lack of interconnection.
Those constraints greatly reduce the difficulty of scaling Mastodon: technical scaling is not a problem if you socially don't allow scale. So distributed you can't even read it.
Doubt is allowed. But from my view, Mastodon world deserves the doubt. It has stood still, barely budged. I'd love to be wrong. But it seems dominated by the one software that is Mastodon, and it doesn't seem to have a universe of interesting connected neat social softwares sprouting up left and right. The software centralization is near to total, the protocol centralization even worse. As a result, there is little distinguishing interesting novel Mastodon technology happening. The one API is deeply rooted. ActivityPub is trying to find some way to get started breaking this mono-culture & enable innovation but that's just started.
Meanwhile a casual glance at Atproto shows hundreds of amazing apps and systems and clients springing up, from amazing empassioned developers. 2025 saw a massive amount of technical decentralziation. Npmx and Eurosky setting up sizable idependent public/public-ish PDS instances, and has shown people indeed moving their core identity off BlueSky servers at some kind of scale. I forgive you for not knowing how far things have come, and I forget myself how incredibly quickly it's come together. It's still 99.99% Bluesky concentrated hosting, but it is distributed, has independent services for the full network, there is credible exit (1000 moved to npmx hosting in the past ~3 weeks), and to me the most important thing: there is technical diversity & independent exploration. There are so many devs building amazing things. That feels so so so absent on Mastodon.
That's the checkbox at the end of the Fermi great filter of interest for online social systems for me: can we permissionlessly build interesting social systems & experiences with these social protocols, or will each system have to look like a cookie cutter copy of a single instance?
This isn't accurate tho.
Neither Bluesky, nor other ATProto services require any of this.
RedDwarf is an example of an ATProto client that connects only with your PDS, uses Microcosm (https://www.microcosm.blue/ )'s aggregation index (they calculate aggregate counts for a variety of things with a couple of raspberry pis run off of a home fiber connection): https://reddwarf.app/
No big iron anywhere in the picture.
You give up the ability to search the network, but okay, that's already a feature that all Mastodon users sacrifice as well.