Even more than the functional requirements, the hardest quality requirements are those that influence key architectural decisions. Therefore, make sure that the most important qualities are very clear to the development team very early on, otherwise the wrong architectural decisions may be made for early versions of the product that are difficult to change later. For example, security can be difficult to build in later, and scalability may also be threatened if you haven’t thought of it in time. For example, you can start building the first floor of a house, but you should know that there will be 17 more floors on top of it.