When running our integration tests (AWS using boto3) we have to enter our MFA code many times, I'm assuming this is because of the multiprocessing/multithreading ? Is there a way to cache these for use across all tests?

Is it possible to use STS/instance profile credentials instead to grant access vs manually entering an MFA code?

Yes. This is more of a boto3 thing rather than a pants thing. Take a look at this thread https://pantsbuild.slack.com/archives/C046T6T9U/p1652807217373179 I feel this is very similar to the issues you might be having

Another option, we actually package some of our integration tests into a single pex_binary with a pytest entry point and run the PEX. The strength of dep inference but relocatable tests