I also thought WhatsApp is a bad example. They not only hosted themselves, but they used solely FreeBSD (as far as I know) in their servers. (which don't get me wrong, I find great as a FreeBSD sysadmin myself).
Using WhatsApp as an example of a lean engineering org should almost be banned at this point. WhatsApp had a high performing engineering team that used basically the perfect set of tools to build their application (which also had a narrow feature scope; plaintext messaging). Even with hindsight there is very little you could do to improve on how they executed.
Just because WhatsApp scaled to almost half a billion users with a small engineering team doesn't mean that's the standard, or even achievable, for almost all teams.
Just because WhatsApp scaled to almost half a billion users with a small engineering team doesn't mean that's the standard, or even achievable, for almost all teams.