i’m very glad to hear we’re considering using the pex cache!!! i feel like benjy probably answered the question here but one interesting point is that as benjy mentioned, if you want to build an “ipex” file which lazily downloads requirements, it’s possible to use a pared-down form of

pip fetch

(one example is in https://github.com/pypa/pip/issues/7819) to get all the necessary info to build the pex with, without needing to download dependencies. but if we can make use of the normal pex cache, then the speedup of that approach is lessened somewhat, although i am actively investigating this. pip is working on upgrading its resolver upstream, which would potentially change further what is cached across pex runs in the future as well.