There's one more cache that people often run into / get foiled by: various applications like browsers and JVMs also cache DNS responses. In firefox, see about

There's one more cache that people often run into / get foiled by: various applications like browsers and JVMs also cache DNS responses. In firefox, see about:networking#dns , in chrome it's chrome://net-internals/#dns . The JVM infamously doesn't (didn't? is this finally fixed?) respect TTL in DNS responses by default. Each name gets looked up once and then cached for the duration of the java process. This has caused innumerable support issues, particularly with zookeeper, kafka, etc. There's some setting you can use to force it to expire its cache after some number of seconds, but as far as I know you can't tell it to just honor the TTL from the response. There's a reason that this poster exists https://www.cyberciti.biz/humour/a-haiku-about-dns/ https://www.cyberciti.biz/humour/a-haiku-about-dns/