Trying to find zip codes/rest example

[VanL]

Hello,

A couple months ago there was an example posted in a blog of a rest 
interface for validating zip codes.  If I recall correctly, the backend 
validator was written in python.

The validator demo page had a single text input; next to the text input 
would appear either a green check or a red X depending on whether the 
zip code was valid.

On the backend, the explanation of the demo included a discussion of 
using HTTP status codes (200 for a valid zip, 406? for invalid) so that 
the service could be used from a console as well.

I now cannot find this demo and the associated discussion.  Does anybody 
remember this demo and where I might be able to find it?

Thanks,

VanL