Since years, our Open Source mORMot framework offers several ways to work with any combination of arrays/objects documents defined at runtime, e.g. via JSON, with a lot of features, and very high performance.

Our TDocVariant custom variant type is a powerful way of working with such schema-less data, but it was found confusing by some users.
So we developed a new set of interface definitions around it, to ease its usage, without sacrificing its power. We modelized them around Python Lists and Dictionaries, which is proven ground - with some extensions of course.