There’s good reasons for adopting Mongo, I’m unconvinced (but open-minded) that performance is one of them. Here’s a ROFLMAO viewpoint on it:
“If your write fails, you’re ****ed”
Obviously, MySQL’s not perfect, but in most cases I’ve seen, it’s been lack of competence on the developer side, and the lack of basic DBA skills – not problems with MySQL itself – that’s broken scalability. In which case, I’m a little suspicious that a company that fails to scale MySQL will equally fail to write their code correctly on Mongo. In many ways, throwing away SQL makes it much easier to prevent scalability…