That's really interesting. The two folks from Facebook contradict each other when talking about joins. Aditya says "No joins in production.", while Mark says "Some of the stories I read about sharded SQL state that you don't do joins when you have sharded MySQL, and that has never been the case for the workloads that I watch. You're always doing some complex query processing within a shard."

Anyway, I can see how you might have come away with the notion that MySQL is a glorified key value store by watching the first video which only briefly touches on their MySQL usage.