I have noticed that there is a lag between the time a question is added to the site and the time it appears on the main page. It is usually only a couple of seconds, but it may be as long as a few minutes? Anybody know why this is?
The canonical answer is always: caching.
That said, we have implemented a live update feature for various and sundry pages on the site. The homepage, however, is still subject to a degree of caching.
We're gradually moving towards more and more live updating on our sites. It used to take several minutes to have a new question appear. Now, it takes several seconds. That's pretty good by my estimation!