[risyachka]

League of Legends chat, WhatsApp and early versions of Facebook chat were build with XMPP and Ejabberd and they were able to handle massive loads with it.

Obviously for an internal company chat app this is not the best option as it will require some maintenance, and the app support is not great, though there are some good options now.

But for heavy chat load it is a great choice that will save you a ton of money, time and resources.