Thanks for the feedback, Robert!

> Under what circumstances, if any, can keys and values in dataTable be unboxed now?

AFAIK there are no specializations for Map/Set. So, the only case when the value is stored locally should be Smi.

And, indeed, there are some opportunities in terms of specializations for primitives and other optimizations in the current implementation. Hopefully, V8 team will find some time to address them in the future.