The key word there is entire. They do not use exclusively NoSQL storage technologies. They use a mix of NoSQL and SQL. There are tradeoffs to each, and if you h

The key word there is entire. They do not use exclusively NoSQL storage technologies. They use a mix of NoSQL and SQL. There are tradeoffs to each, and if you have as many really, really great engineers as such places employ, it can make sense to deploy whatever database technology best suits each narrow storage problem in order to meet absurdly high levels of usage. For 95% of us, who have neither the resources or the needs of a business that large, using a relational database for everything is probably the right choice.