Cynical tone aside, there’s a good question here. It’s just that the question has an actual, valid answer: it’s impossible to have a single database that operates at Twitter scale.

If you think it is possible to have a single database that operates at Twitter scale, fine, there’s probably an interesting and enlightening conversation to be had about how and why that is or is not the case.

Continue along this vein and you eventually you get to the point where you’re discussing realistic solutions, and maybe at the end of it you’ve either gained an understanding of how these things work or else you’ve actually come up with a better system design than Twitter. Either way you’ve gained something more valuable than the petty satisfaction of disparaging other people’s motivations.