Yes, cold starts is a surprisingly stubborn problem that has many layers. We got it down to 100-200ms. Recently as we move compute from containers to VMs we starting to see more missed so we regressed it a bit.
It is theoretically possible to get it to 50ms range.
You guys have done a good job with Neon so far and ~200ms is good enough for 95% of webapp use cases (especially if devs do things like optimistically wake up the DB when a user hits the landing page or login page).
I'd be interested to see if you guys can hit 50ms without keeping more chunks of data in at least lukewarm memory. That probably comes at an increased baseline running cost for that database. Maybe customers would be willing to pay a bit extra to enable "turbo" cold starts for the databases that would benefit from it.
It is theoretically possible to get it to 50ms range.