Telegram is amazing messaging app. It is so fast! When I travel by boat and my phone barely sees one notch of GSM service (not 3G, not even Edge) from the island on the horizon - Telegram is able to send and receive messages. Whatsapp and Slack can't even connect for hours after that.
Another amazing thing is when I type a message on my phone - I see it on my PC the moment I press Send button. There's no visible delay, a perfect Google search effect from 2000-s.