Based on cloudflare's own blog[0], 1% of queries went unanswered for about 10 mins, and were significantly delayed for a few hours. 5% of queries were delayed for a couple of hours. 95% of queries continued to be resolved as normal.
This is referring explicitly to users of 1.1.1.1, which is likely not the same infrastructure as domains hosted by cloudflare dns.
[0] https://blog.cloudflare.com/october-2021-facebook-outage/