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Comment by nodesocket | Hacker News Reader

> DNS TTL is a lie. Even though we have TTL of one minute for www.dropbox.com, it still takes 15 minutes to drain 90% of traffic, and it may take a full hour to drain 95% of traffic.

Interesting, awhile back both Google and AWS engineers replied to a HN thread[1] saying TTL of 30 seconds or so works pretty responsibly and can be trusted and used. Seems to be some disagreement on this.

[1] https://news.ycombinator.com/item?id=17553043

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It really depends who your clients are. If they are servers, 30s can work okay. If they are end users, caching happens all over. It's a huge PITA, especially since you'll run into podunk ISPs that have their own custom caching setup, but you have a customer with a shop there. Not that I'm still bitter.

It really depends on the clients, here is an excerpt from the article:

> Here we also need to mention the myriad embedded devices using Dropbox API that range from video cameras to smart fridges which have a tendency of resolving DNS addresses only during power-on.

> which have a tendency of resolving DNS addresses only during power-on.

Facepalm...

DNS TTL is a PITA for us at Netflix as well. We use Zuul to proxy cross-region for TTL "non-responders".

It would be funny if part of what they are seeing is because the Dropbox client doesn't try reconnects or re-resolving very often.

There's a lot of caching done by e.g. Comcast that does not always honor the TTL.

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