Web applications are made of more and more external packages and libraries. It's easy to pull "free stuff" from the Web, but is it as easy to maintain a big project composed from random dependencies? Based on my experience with enterprise-grade payment systems I will tell you how we ensure the security of our applications, how we pick the best libraries and how we avoid being sued for copyright infringement. You will learn software development driven by a reliable analysis and not just hype, Stack Overflow and GitHub stars.