What's the Logic for In App Purchases?

Just wondering what the best or recommended way to code for unlocked items when using in app purchases?

I'm not asking how to code for in app purchases, but rather, what the logic is after the user has bought something?

So, if the player bought something and the time is now unlocked, how do you code or that?

Do you use player prefs, or is there another way or a better way to go about this?

Thanks.