> we brought down image creation time to mere seconds, even for images that were multiple GiB in size

this sounds interesting; for e.g., was wondering the other day if we could build images without actually pulling base images.. everytime we compile, we copy artifact(s) onto a multi-hundred MB base image which definitely doesn't need to be pulled everytime.

You absolutely can just build things and put them on base images without building or pulling the base image at any point. This is a central feature of ko, a simple container build tool for most Go applications: https://ko.build

(I am a maintainer)

There are many ways to achieve this. If you are just copying artifacts, and not using RUN, then there is in principle no need to download the base image at all. Feel free to message me if you'd like to chat (email is in my profile).

You can, by using FUSE and lazy pulling files as they are opened. I'm working on doing this, myself.