H̶a̶l̶f̶ ̶a̶ ̶b̶i̶l̶l̶i̶o̶n̶ 600M unsuspecting FreeBSD users
youtube.com
youtube.com
The important takeway is that FreeBSD and Erlang have worked really well for WhatsApp allowing them to grow their userbase insanely fast while still staying relatively small.