How does mailchimp cache?

[Neil]

We're using the API and running into a problem with mailchimp
occasionally emailing out old content in test emails after we make
changes and try to send a new test. In between each test email, we
delete our old campaign and create a brand new one, but we're still
seeing old content being emailed out. We import content via URL and
have verified that the content at our URL is correct and up to date.

I can only assume that Mailchimp is caching the content and sending
out the cached version. How does the cache work? What are its keys?
How long does it last? Is it possible to explicitly clear the cache
through the API? It seems like a bug that a fresh campaign could hit
cached content.

We have lately been experimenting with generating fresh URLs after
each edit as well, in addition to the fresh campaign, in an effort to
avoid the cache. This sometimes seems to help but doesn't appear to be
foolproof. We have noticed that changing the subject line of the email
also seems to help, but I can't really say definitively.

Thanks for your assistance!
Neil

[jesse]

For the specific case of Campaign Content of type "url", cached
content is cleared when the url is updated either via the web app or
the API. We also cache the md5 sum of the content and will only update
the cache if the new md5 sum doesn't match. That check is done anytime
the campaign's content is requested (various content related api
methods, sends, popup previews in the app, etc).


jesse