might also be worth noting that rankmirrors, while very useful for finding the fastest mirror, does nothing in regards whether that mirror is fully synced with the central repo.
see here:
https://archlinux.org/mirrors/status/
"Completion %: The number of mirror checks that have successfully connected and disconnected from the given URL. If this is below 100%, the mirror may be unreliable."
which is what i meant by "laggy mirror"