Its extremely difficult to cut over millions of lines of code and 15+ years of development. We are working on it, but the db was never properly sharded and that

Its extremely difficult to cut over millions of lines of code and 15+ years of development. We are working on it, but the db was never properly sharded and that is very difficult to do at a late stage. When you work on big enough projects the common sense approaches break down. FB messager doesn't use MySQL, Amazon shopping cart doesn't use Postgres. There is a reasons why. This isn't a wordpress app, it needs to process 10s of thousands of updates a second and still be a responsive app with 99.9% uptime and low SLAs on requests.