I used to be strongly in favor of using fixed versions everywhere, but now I also have a mixed opinion. I think a reasonable compromise is to continually updat

I used to be strongly in favor of using fixed versions everywhere, but now I also have a mixed opinion. I think a reasonable compromise is to continually update and to promote images. That way you can start with `dev --> prod` when you're small and add more QC layers as things grow. Something that's even more difficult is dealing with upstream changes. What do you do when `ubuntu:18:04` updates? It's easiest if the upstream is released with a predictable cadence (ex: every Wednesday), but none are AFAIK. That way you could plan a routine where you regularly promote an update through QC. I'm not sure what to think about event driven release engineering like auto-builds (repo links) on Docker Hub. I think that might be an ok solution for development builds or rebuilds of base containers, but it seems to be abused. I bet there are maintainers of popular images on Docker Hub that are effectively triggering new deployments for downstream projects every time they publish a new image.