Why updating DNS is slow

As as aside, I recently goofed up our company website DNS (updated a record on long TTL with an incorrect), but quickly fixed it and found a partial workaround to propagation: flush the DNS cache of Google[1] and Cloudflare[2]. It helped with DNS cache refresh within minutes from most global locations, if not all.<p>[1] <a href="https:&#x2F;&#x2F;dns.google&#x2F;cache" rel="nofollow">https:&#x2F;&#x2F;dns.google&#x2F;cache</a> [2] <a href="https:&#x2F;&#x2F;1.1.1.1&#x2F;purge-cache&#x2F;" rel="nofollow">https:&#x2F;&#x2F;1.1.1.1&#x2F;purge-cache&#x2F;</a>

Would be nice if they didn&#x27;t stomp on real addresses.<p>&gt; The blocks 192.0.2.0&#x2F;24 (TEST-NET-1), 198.51.100.0&#x2F;24 (TEST-NET-2), and 203.0.113.0&#x2F;24 (TEST-NET-3) are provided for use in documentation.<p>-- RFC5737 <a href="https:&#x2F;&#x2F;tools.ietf.org&#x2F;html&#x2F;rfc5737" rel="nofollow">https:&#x2F;&#x2F;tools.ietf.org&#x2F;html&#x2F;rfc5737</a>

Hmm.. now I realise that &#x27;live&#x27; in &#x27;time to live&#x27; is &#x27;live&#x27; as in &#x27;life&#x27;, not &#x27;live&#x27; in the &#x27;going live&#x27; sense ... It&#x27;s the record&#x27;s cache time! Engineering&#x2F;techy acronyms are a bad place for homographs...

There are two types of useful documentation or training materials.<p>1. The detailed and accurate type which covers everything you need to know and takes time to work through and gather the parts you need to learn.<p>2. High level gists which share only the basics you need to gather the intuition for the space. This type helps make learning from the first type easier. These comics are the second type. I ran through the questions for TLS and found them helpful. I had so many questions a few months ago and these types of resources are so good for getting you to asking the right questions.

Once you do a (planned) migration of a few sites, you quickly learn to set the DNS TTL to something small beforehand. Alternatively (if possible), keep both IP blocks active for the TTL duration.

I wonder how relevant &quot;long&quot; TTLs (5min, 30min, etc.) still are in an age of massive multi-gigabit fiber links? DNS was invented long ago, a very simple protocol with a handful of bytes per packet - a trickle amid the torrent. Waiting an hour or more for a 4-byte change (an IPv4 address) to be committed to a distributed database seems incredibly antiquated.

Not too bad! Covers the major things most forget when trying to understand this question.

In my experience, updating DNS is surprisingly fast, even though I typically set my TTLs to 3 hours. Typically I don&#x27;t have to wait more than 2-5 minutes. Faster than e.g. updating an avatar on GitHub.

This problem is pretty much fixed in Firefox. The cloudflair doh server updates records very quickly. Also has the side effect of unblocking the pirate bay for me.