The world was a better place with Jabber/xmpp where we could setup our messaging system and don't rely on closed systems like we do today as Whatsapp, Telegram, iMessage, etc. iirc Google deprecated support for it in Google voice long time ago which marked its declined
Something that I recently have explored is the optimization of Docker layers and startup time for large containers. Using shared storage, tar layers preload, overlayBD https://github.com/codeexec/overlaybd-deploy is something that I would like to see more natively. Great article