Quad9 does not currently offer a public, cache flush tool. There are various technical and security limitations that prevent Quad9 from offering this feature at this time.
Quad9 does not honor cache flush requests submitted to our support team.
Quad9 is working with our open-source software partner to make the necessary performance and scaling improvements to the code base to be able to support this in the future.
Before making major changes in DNS, such as changing authoritative DNS services, a standard practice is to lower the TTL significantly of the modified resource records and allowing enough time to elapse for the previous TTL to expire, thus providing the opportunity to revert the changes with limited impact in case of misconfiguration.
In the future, Quad9 may be able to offer a cache flush tool or honor cache flush requests submitted to our support team, but there is no timeline for offering this feature.