Is this the same comic that (appeared in newspapers yesterday|will appear in newspapers today)? If so, he said in a blog post a few months ago that the normal lag is ~a month and the best he could do was like 2 weeks. (Those numbers are a little off, I'm sure.)
But if this is just an online version (it is /fast, whatever that means), it might be a different story.
AFAIK /fast is an URL to read just the comics "fast" without spending bandwidth loading all the additional information presented in the landing page of the website.
FWIW, the previous comic to this one in that website, labeled July 14th, was in yesterday's July 14th newspaper here (Yes, I'm from Sydney Australia, we live _in the future!_ aka UTC+10)
But if this is just an online version (it is /fast, whatever that means), it might be a different story.