[stopthe]

Having dealt with similar architectures, I have a hypothesis on how this library (Hollow) emerged and evolved.

In the beginning there was a need for a low-latency Java in-process database (or near cache). Soon intolerable GC pauses pushed them off the Java heap. Next they saw the memory consumption balloon: the object graph is gone and each object has to hold copies of referenced objects, all those Strings, Dates etc. Then the authors came up with ordinals, which are... I mean why not call them pointers? (https://hollow.how/advanced-topics/#in-memory-data-layout)

That is wild speculation ofc. And I don't mean to belittle the authors' effort: the really complex part is making the whole thing perform outside of simple use cases.