@kwf I used to and regretted it to no end, because (to my imprecise observations) it can cause havoc if you have a non-static machine (aka laptop) and/or VPN. So if 'fastest' changes, and DNF and the net do not agree, fun ensues. My 2cts (that may be inaccurate). I now leave it to default, and try to limit dnf in general to core libraries, with user space provided by flatpak, so less use case in optimizing it.

@kwf I've variously had it on and off, but it's never seemed to work very well to begin with.

@kwf It does help in India. Because they are no Fedora mirrors and they geo route to Japan and China because it is physically closer.
But routing to those countries from Indian ISPs is usually through USA and everything ends up very slow with high latency.
On the other hand, European and American mirrors are faster.

@kwf I wish it didn't exist. People turn it on thinking it's a magic 'go faster' button, but it just sends you to the mirror with the lowest latency, which is very often not the mirror that has the fastest actual downloads. ;(

@kwf I’ve often thought surely the best thing here is if the package manager load balanced across _multiple_ mirrors at a time and then worked out the best one to use automatically. I don’t use fedora but Ubuntu gets it wrong too - the CC DNS CNAMEs always end up giving me less than ideal performance. Even better, have the package management client download files from multiple mirrors for a single file with range requests (if larger than a certain size). There’s got to be some good heuristics you can derive from that!