> This means a worker running in the same data center hosting your D1 databases might get ~10ms requests

This is already waaaaaay too much. Same datacenter I expect nano seconds round trips. Datacenter to a datacenter on the other side of the world? Maximum 300ms. It was what you expected of game servers two decades ago. I don't see what could eat more than a couple dozen ms on the server with current hardware to make a 10ms round-trip become "> 200ms" and consider this a service you'd pay for.