I've found in multiple projects that accessing process.env within a hot section of the code leads to major slowdown.

This really hurts in React server-side rendering (issue) and has caused them to rearrange how they access the env.

It would sense to cache already-accessed properties rather than reaching out to the actual environment. And of course, update the cache on assignment.

I would be happy to contribute a patch if anyone could point me in the right direction to get started, as I'm new to Node core dev.