It does not exist in software design, web design or business in general.
Perfection is something we all strive towards, but if you delay a product, site or business launch until everything is perfect you will never launch it.
I launched LogoGround almost 5 years ago. Most of it works perfectly and it is doing exceedingly well. There are also many things that don’t work perfectly. We have a to-do list with bugs and ideas for improvements. It has 91 entries. We are adding new items to the list faster than we are fixing old ones. This is a good thing. It is the way you work towards perfection.
Set your launch deadline and stick to it.