The Type-Safe-Boundary, what it is and how to use it to prevent bugs

Background

I’ve been writing code for some decades now. Over that time there is one thing I have learned through projects that have failed, projects that have been successes, legacy projects, greenfield projects, projects with dedicated experienced teams, projects with fresh new developers, distributed projects, closed source and open source, and all other kinds, being a consultant working with a multitude of companies and open source enthusiast, and that is - strongly typed code prevails.