I have a website that has similar functionality to Stack Overflow where you can click on favorite grey star and it turns yellow (swaps images).
It seems like on Stack Overflow it changes instantaneously where on my site I change the image on the callback from an ajax post so it takes a second for the server to commit and then the callback to fire on the client side. I use a loading ajax image in the meantime so its fine but i am trying to figure out if:
Stack Overflow changes the image before an ajax post and just assumes it will commit successfully.
The site is just that fast that it returns so quickly and updates on a callback.
NOTE: I am preloading images, etc.