Disabling windows search indexing on your work folder and yarn cache folder as well as disabling windows defender completely or on a folder should give you significant performance boost. I’ve got 30-50% decrease on similar system with SSD drive, originally timings were as yours.
Disabling it on Yarn cache folder would also give you some speedup. Its location is shown by yarn cache dir command, %USERPROFILE%\Local Settings\Yarn\cache by default.
To disable search indexing on a folder, find it in Explorer, right click, then Properties – General – Advanced, uncheck the “Allow files in this folder to have contents indexed in addition to file properties” checkbox, then Apply the changes.
This performance issue already exists on yarn github (Oct’2016) and is still open to the moment: https://github.com/yarnpkg/yarn/issues/990