WhatsApp for one: http://highscalability.com/blog/2014/2/26/the-whatsapp-architecture-facebook-bought-for-19-billion.html http://highscalability.com/blog/2014/2

WhatsApp for one: http://highscalability.com/blog/2014/2/26/the-whatsapp-architecture-facebook-bought-for-19-billion.html http://highscalability.com/blog/2014/2/26/the-whatsapp-archi...