I have moved my blogs to my @OpenBSDAms VM, as I need that 1 euro small VM for some tests (spoiler: chatmail server for Delta Chat). The DNS TTL is set to 300 seconds, which is 5 minutes. After more than 30 minutes, some hosts are still connecting to that old record.
I agree with @nuintari - the problem usually isn't the DNS but the MISCONFIGURED dns. And it's full of them, out there.