The way that instances connect to each other is O(n^2), which is not to say it's exactly n^2 but the curve is of that shape. This isn't strictly a problem with

The way that instances connect to each other is O(n^2), which is not to say it's exactly n^2 but the curve is of that shape. This isn't strictly a problem with ActivityPub as with how it's used, especially in Mastodon. It's why you keep hearing about super-long queues chewing up RAM, and causing long delays - hours or even days - before content appears. It's why Mastodon instances tend to be clusters of larger machines at a scale that you would think can be served by a single smaller machine. The usual solution for this set of problems is connection and/or request aggregation via a proxy layer. Relays (in fediverse-speak) do exist, but seem very lightly used and do little or no caching because ActivityPub relies heavily on POST (which IMO was probably a bad decision). Any caching that's done has to be ActivityPub-specific. I wrote about this a while ago and almost certainly got some stuff wrong, but it might be interesting nonetheless. At least it drew some interesting comments at the time. https://gist.github.com/jdarcy/60107fe4e653819138396257df302eef#file-activitypub-md https://gist.github.com/jdarcy/60107fe4e653819138396257df302...