Well, he didn't do that. He just wrote a crappy basic PHP backend. The "scaling at Facebook scale" part happened later, after people were hired and VC money flew in.

Same like early Twitter was a crap Rails app that they even had to restart a few times a day because of memory leaks. It still got them through to attract users (even though it crashed all the time) and money, so they eventually were able to fix that and grow to Twitter scale.

None of those things happened because of very talented hacker founders. Those kind of apps aren't even very technical or different to the average CRUD app - not until the scale/infrastructure people come in much later: those do the actual hard work.

Cloudflare, Redis, SQLlite, Nginx, ElasticSearch etc, on the other hand, are a different story. Those are absolutely apps/platforms made from scratch by seriously talented hackers, even if others were involved to improve them later on.