People should be aware that adding additional mirrors (instead of switching mirrors as suggested here) can lead to big slowdowns, as pip has no way to determine

People should be aware that adding additional mirrors (instead of switching mirrors as suggested here) can lead to big slowdowns, as pip has no way to determine whether a given / found wheel is the m best choice without comparing all options, so it will continue to search both locally and all available indices until it can resolve the "best" wheel to download. Some discussion: https://discuss.python.org/t/why-does-pip-reach-out-to-indices-when-a-local-file-is-available/8920 https://discuss.python.org/t/why-does-pip-reach-out-to-indic... I don't recall if this issue is solved by specifying hashes (or perhaps even pinned versions are adequate) -- I would hope so.