WhatsApp scaled to 1B users with only 50 engineers
While what you says about focus is important, I've seen plenty of focused startups die.WhatsApp had success because they executed well enough at the right time.I hate WhatsApp with passion because of its limits and that horrible web interface that needs your phone connected in order to work.I know plenty of people (me included) who stopped talking with some groups of people because they didn't tolerate WhatsApp.It's mediocre software at best, but because of the network effect and first mover advantage, that was enough.