Joe -
I'm really grateful that Rederly is sharing this, so the community can hear about what can be done with WeBWorK at scale.
Could you share some basic explanation of what roles the "back-end" handles, and what is being stored in the database (as I understand that Rederly does not use the standard WW databases at all).
I suppose that the "back-end" is Rederly's alternative to both some of the higher-level management functions provided by the "webwork2" layer of WW for "standard" WW systems and also a "broker" receiving web requests and creating the relevant calls to the PG problem "renderer".
To what extent can a "renderer" container interact directly with external systems without such a "back-end" or with a very minimal "back-end"? The long-term motivation for the question is how to best provide an "html2xml" like interface for embedding WW questions in web-pages of various sorts, MOOC courses, electronic textbooks, etc. which can support "scale" (possibly at the expense of sacrificing keeping records of answers submitted, etc.).
Would Rederly be able to share Docker files, etc. explaining what is in each image or at least in the renderer image, and any custom code needed for the rendered Docker image?
At present, I am focused on other things, so I will not be following up much at present on the scale issues/ideas, but will try to participate in the discussions.