Ask HN: Resources for learning how to secure a machine learning API

All courses (?) for deploying ML APIs assume that you don't mind that everybody can access your API if they know the external IP. That works because it's always just toy examples. But how do I learn to actually secure my API so that I can choose who can access it.

I know that GCP Cloud Run and Azure Container Instance offer simple ways of making services private. Both managed solutions. But what about hosted solutions? Where do I learn about that?