Cache Conda env
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> 1. Can `cache-downloads: true` be set?

Yes we can do it. I'm not sure it's worth it given that the total amount of data that can be cached per repository is 10 GB (https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#usage-limits-and-eviction-policy) and some of the envs are 0.5 GB large. > 2\. Could you give an example before/after improvement in the setup?

Sure, here we have 2 min -> 0.5 min https://github.com/pandas-dev/pandas/runs/7000499676?check_suite_focus=true https://github.com/pandas-dev/pandas/runs/7007202415?check_suite_focus=true and here we have 4.5 min to 1.5 min https://github.com/pandas-dev/pandas/runs/6998916048?check_suite_focus=true https://github.com/pandas-dev/pandas/runs/7001171440?check_suite_focus=true

In my experience env setup can be considerably slower if there are network problems. For example here we have 8 min, although I'm not sure how much of it is related to using Mamba instead of Micromama https://github.com/pandas-dev/pandas/runs/7028218282?check_suite_focus=true. > > 1. Can `cache-downloads: true` be set?
> 
> Yes we can do it. I'm not sure it's worth it given that the total amount of data that can be cached per repository is 10 GB (https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#usage-limits-and-eviction-policy) and some of the envs are 0.5 GB large.

I see. I would still be partial in trying it as I've noticed we sometimes still hit connection errors from conda although I extended the timeouts in the `condarc.yml`. If environments are evicted from the cache during every build due to the size then yeah I can see it not being worth it Thanks @jonashaag. These CI improvements are awesome! 