DNS isn't hard to get right. Using DNS practically is the thing that is hard. Is your cache something from NICs, ISPs, routers (and routers behind routers), ope

DNS isn't hard to get right. Using DNS practically is the thing that is hard. Is your cache something from NICs, ISPs, routers (and routers behind routers), operating systems (and operating systems behind operating systems), runtimes like containers (and runtimes inside runtimes), a Docker image that overrides /etc/resolve.conf, and then programming language (and if you're unlucky, a programming language that uses the stdlib of another language instead of the syscalls directly), third party libraries (and fourth party libraries used by third party libraries), or maybe yourself calling the wrong API. Or if you passed the domain name to a distributed system, the problem gets doubled because your distributed system may not share the same stack ... and then you figure out it's actually because the guy who said they updated the DNS record actually updated the A record without updating the AAA record.