> the ability to quickly rollback to a prior known good stage This is vital, but it's often not sufficient just to roll back, say, to a known good Docker image

> the ability to quickly rollback to a prior known good stage This is vital, but it's often not sufficient just to roll back, say, to a known good Docker image. Database migrations may have occurred that dropped columns that the old code expects to exist; feature flags may need to be changed; multiple services may need to be rolled back individually; data may have accumulated under new assumptions that breaks old assumptions when old code is applied to that new data. One of the really subtle wins of devops as a discipline is that by allowing/forcing application teams to take responsibility for deployment, they're more exposed to thinking how to solve these things in a maintainable way: for instance, breaking out complex "the meaning of our data is changing"-type changesets/data migrations into individually reversible stages, with the stages merged onto the production branch over the course of multiple days where analysis is done on error rates and live data.