When performing a system update on a freshly downloaded Arch Linux WSL, the following error occurs.

[himbeertoni@arch-wsl ~]$ sudo pacman -Syu --noconfirm

We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:

    #1) Respect the privacy of others.
    #2) Think before you type.
    #3) With great power comes great responsibility.

For security reasons, the password you type will not be visible.

[sudo] password for himbeertoni:
:: Synchronizing package databases...
 core downloading...
 extra downloading...
 community downloading...
error: failed retrieving file 'community.db' from geo.mirror.pkgbuild.com : The requested URL returned error: 404
error: failed retrieving file 'community.db' from mirror.rackspace.com : The requested URL returned error: 404
error: failed retrieving file 'community.db' from mirror.leaseweb.net : The requested URL returned error: 404
error: failed to synchronize all databases (failed to retrieve some files)

tl;dr

As part of the git migration the [community] repository was merged into [extra]. To fix the error, comment out [community] related entries in /etc/pacman.conf.

#[community-testing]
#Include = /etc/pacman.d/mirrorlist

#[community]
#Include = /etc/pacman.d/mirrorlist

Further Reading