Does a "delegated type" work with preloading associations, ala "includes"? This remains a pain point with many polymorphic associations in Rails, but not sure how the new functionality handles if, if it does at all.
[0] https://github.com/rails/rails/pull/39341#issuecomment-72725...
This sounds counterintuitive; but, in the common case of read-heavy services, N ≐ 0 after the first access. When something changes, subsequent views end up loading & rendering the one record that changed, instead of preloading an entire collection.
However, achieving this in practice requires some care in the nesting of view partials and records.
c.f. DHH in https://www.youtube.com/watch?v=ktZLpjCanvg&t=4m27s "N+1 is a feature"
I don't mind that, since I've chosen to infer an assumption that we're all as smart as he is. (even if it does then take me years to explain things to myself...)
If you didn't find it already, his "On Writing Software Well" video series is a fascinating, and sadly abbreviated, journey into his own application code.