ACID Model
MySQL at least historically didn't support transactions, which in banking, for example, allow you to say "don't add to account B until we're sure we've deducted from account A". You want two things to happen at once, or not at all.
It also didn't do much for keeping track of relational integrity, like saying "every order has to be attached to a customer's record".
I'm not too familiar with recent progress; I just used the name because it's reasonably accurate, and you can find a number of programmers who've done much wringing of hands regarding MySQL.

Dollies, in case you missed that, are something like this. I've usually seen them as four pieces of lumber nailed together with casters or pivoting wheels underneath, which explains using two under a fairly large, rectangular server.

And Rolaids are a brand of antacid tablet.