I have recently discovered that whenever I try to run an update on my arch system, I would get the following error:

error: failed retrieving file 'core.db' from mirror.ubrco.de : Failed to connect to mirror.ubrco.de port 443: Connection refused

This was happening quite a lot in the last couple of days, and it was getting annoying since after restarts, the same updates would appear.

So I spent some time and troubleshooted the issue, to discover that my mirrors were set to Germany for some odd reason.

My fix was very easy, I just run the reflector app to re-scan mirrors and set the first 5 with highest download rating in my mirrorlist:

sudo reflector --verbose --latest 5 --sort rate --save /etc/pacman.d/mirrorlist

Once the process completed successfully, I ran again the update command in pacman:

sudo pacman -Suy

and everything was beautiful again.