We're actually median under 500ms — ~320ms median — I just didn't want to piss of hacker news with over estimatation.

We have another set of optimizations that we believe can take us to ~200ms in the next few months but beyond that we're pretty much completely stuck.

Realistically other sandboxes will be able to get there before us because we've chosen to support so much of Linux/if you don't run an operating system or don't support custom snapshots that is much easier.