is_file_on_ssd() on Windows uses a cache to avoid repeated checks whether a given volume is on SSD.

However, it still uses GetVolumePathName() to retrieve volume for any given file.
GetVolumePathName() appears to be expensive, procmon shows that internally it opens every directory in the hierarchy, probably to check whether directory is a symlink.

This can be improved by using volume serial ID as cache key instead, it is cheap to retrieve it for an open file.