Today kbin.social is blocking a huge list of domains just to get federation working again.
The reason for this temporally block is not to defederate, but rather to get the large backlog of 500k messenger queue processed again. Anyway, this does mean that kbin.social is federating again with other instances.
This is a temporary measure. Several users / developers are looking into how to better optimize the failed message queue, as we speak. Hopefully Ernest has eventually time to dive into solutions as well instead of workarounds, once his instance is migrated to Kubernets. See my preview thread: https://kbin.melroy.org/m/updates/t/4257/Kbin-federation-issues-and-infra-upgrade
List of the domains causing trouble:
lemmygrad.ml, eientei.org, vive.im, lemmy.ml, lemmynsfw.com, kbin.lol, lemmy.webgirand.eu, tuna.cat, posta.no, lemmy.atay.dev, sh.itjust.works, kbin.stuffie.club, kbin.dssc.io, bolha.social, dataterm.digital, kbindev.lerman-development.com, test.fedia.io, mer.thekittysays.icu, lemmy.stark-enterprise.net, kbin.rocks, kbin.cocopoops.com, kbin.lgbt, lemmy.deev.io, lemmy.lucaslower.com, lemmy.norbz.org, social.jrruethe.info, digitalgoblin.uk, pwzle.com, lemmy.friheter.com, federated.ninja, lemmy.shtuf.eu, u.fail, arathe.net, lemmy.click, thekittysays.icu, lemmy.ubergeek77.chat, lemmy.maatwo.com, faux.moe, eslemmy.es, seriously.iamincredibly.gay, test.dataharvest.social, programming.dev, kbin.knocknet.net, pawb.social, lucitt.social, longley.ws, kbin.dentora.social, atay.dev, lemmy.kozow.com, ck.altsoshl.com, pawoo.net, techy.news, lemmy.vergaberecht-kanzlei.de, lemmyonline.com, beehaw.org, pouet.chapril.org, kbin.pcft.eu, fl0w.cc, lemmy.sdf.org, lemmy.zip, feddit.dk, fedi.shadowtoot.world, lemmy.noogs.me, lemmy.kemomimi.fans, social.agnitum.co.uk, fediverse.boo, hive.atlanten.se, forkk.me, lemmy.ghostplanet.org, lemmy.mayes.io, lemmy.mats.ooo, lemmy.world, lemmy.sdfeu.org, lemmy.death916.xyz, geddit.social, masto.fediv.eu
So it’s two-fold: the underlying technology and the amount of data it can handle.
Expect growing pains as they (the instances) find tech that works.
The underlying technology has quite some down-sides indeed (activitypub) in terms of scalability. At the same time, large/big instances of the fediverse need to process large amount of data (not only local data but also external data from remote instances). Plus /kbin was still in early development phase, not fully ready to scale yet, so it was a big unexpected (due to Reddit ...) migration. All the things I just mentioned are now coming together, all at once.