This is basically "We made it work, easy, all the rest are wrong". Wix is 10 years old, they probably started with MySql and stuck with it, is it wrong? Maybe, maybe not. If they were to start today would they have used Mysql aswell or gone with another solution? Did they spend the last 10 years building tools to help them scale MySql (at which point it's easy for them to operate) rather than use a tool that had mult…
Uber built something similar in the last couple of years.
https://eng.uber.com/schemaless-part-one/
So did Dropbox.
https://blogs.dropbox.com/tech/2016/05/inside-the-magic-pock...