you're right that that's the slow bit (typically about 50ms to set up each channel, so across 1000 devices that's 5s to establish the initial mesh), but the imp

you're right that that's the slow bit (typically about 50ms to set up each channel, so across 1000 devices that's 5s to establish the initial mesh), but the important thing is that having established the channels, they are only used to sync key data for the megolm layer which sits on top. megolm keys typically rotate every 100 messages or every day (whichever comes first), and this uses the existing olm channels. In turn, the olm channels themselves only resetup when conversation changes direction (or if they stall). https://blog.jabberhead.tk/2019/03/10/a-look-at-matrix-orgs-olm-megolm-encryption-protocol/ https://blog.jabberhead.tk/2019/03/10/a-look-at-matrix-orgs-... is quite a good overview of this (from the XMPP perspective!), as is https://www.uhoreg.ca/blog/20170910-2110 https://www.uhoreg.ca/blog/20170910-2110 (from the Matrix perspective).