Earlier quoted context omitted.
Strange take when FB, twitter, Square and new startups such as Faire(#4 valued private YC co) are all using MySQL to some/large degree. Stripe uses MySQL too in combination with other DBs including Postgres.
You're not considering the timeline of events. I'm unfamiliar with Faire but the rest were already using MySQL at the time of Oracle's acquisition in 2010. Switching backends would have been rough for those companies and this was... 2010, meaning Postgres was not nearly as performant or full featured as it is today. As mentioned in other comments, FB's investment in customizing MySQL has been extensive. They've poure…
I don’t think either DB is bad, but the whole MySQL is dead and needs serious work idea doesn’t make sense to me. What problem does MySQL still have that needs fixing in your opinion?