I gave up their dns quite long ago, I was getting slow internet regularly and some day I discovered accidentally that it was their fault.
It’s interesting that the internet is packed with search hits of complains that Cloudflare’s DNS is slowing everything but Cloudflare representatives are quick to post followups pointing the finger everywhere else.
That’s like the most trivial of theories one can test for.
Save response time every minute
while true; do /usr/bin/time -f "%e `date`" dig '@1.1.1.1' +noall programming.dev &>>/tmp/dns_clf_perf.txt; sleep 60; done
Then after a while (maybe a couple of days), check the worst numbers:
sort -n /tmp/dns_clf_perf.txt |tail
Run the same script with a different DNS server at the same time, and compare numbers.
Dates included in case there are any patterns regarding the time of day/week.