Yes, you can limit both challenge types and account URIs in CAA records. To revoke the record, delete it from DNS. Let’s Encrypt queries authoritative nameserv

Yes, you can limit both challenge types and account URIs in CAA records. To revoke the record, delete it from DNS. Let’s Encrypt queries authoritative nameservers with caches capped at 1 minute. Authorizations that have succeeded will soon be capped at 7 hours, though that’s independent of this challenge.