Twitter is doing something vastly more technically challenging that WhatsApp.  WhatsApp just delivers messages.  It doesn&#x27;t store them, and it certainly doesn&#x27;t, say, try to make them available in a searchable away to everyone in the world.<p>This isn&#x27;t a knock on WhatsApp -- I use WhatsApp and don&#x27;t use Twitter -- but Twitter&#x27;s scale challenges are vastly more complex than WhatsApp&#x27;s, which doesn&#x27;t have many features that can&#x27;t just very simply horizontally scale.