When Do You Start Thinking About Monitoring When You Are Building a New Service or System?

When do you start thinking about monitoring when you are building a new service or system? Or i guess in your experience, i know monitoring is a corps component of what you focus on. Is that something that you then apply, you bring your approach to existing systems and involve that monitorin ours this? I don't know. I guess when do we think about it when it doesn't exist yet, or when d we think about when to up date it? So during any development process, there's one step, which is verification, right? Even after pushing this new feature to prod, you still have to check if the feature is actually working as intended for everybody.