I think I already said I love this mod, but I'm saying it again.
I've been working support for it into my own mods, and learned something worth sharing that the example modification pointed to by the author doesn't cover:
You have to invalidate your own cache. It's easy enough to do, just set it to blank and the mod takes care of it for you, but things won't work if you don't.
As an example, if you are caching the eggs that are on an avatar, when someone throws a new egg at said avatar you have to invalidate the cache for that query or the new egg will not show up.
It's important when writing support for this mod that you consider all your invalidation scenarios.
Also, you cannot invalidate vBulletin data (without a lot of work I assure you that you do not want to do). So if you have a query that, for example, gets the users last login date, you can't cache that. Fortunately vbulletin does it's own cache to some extent, and vb Optimise does more, so just hope for the best on volatile vBulletin data. It's out of your hands.
PHP Code:
$optimise->set('mycachekey', '');
Is all that's required to invalid cache. 'mycachekey' of course being the key to the cached item you need to invalidate.