[jasimp]

I can guarantee you that popular DNS resolvers (think 500b+ transactions a day) do have this feature!

Don't want to say much more due to it being my job, and I don't want to give away too much.

EDIT: https://www.google.com/patents/US8583801

[imsofuture]

What is the point of this comment?

[bhauer]

FWIW, since the comment was a reply to my message above:

It provided value by answering my question concerning serious downsides to providing optional post-TTL last-known-good caching within a DNS resolver. The answer is implicit in that a major DNS resolver provides exactly this functionality.

[jasimp]

Thank you :)

A little more information, considering it is public. (I had to double check if it was)

https://www.google.com/patents/US8583801

[pyvpx]

you mean opendns?

[jasimp]

No I mean ISP's that run their own DNS resolvers.