App development is inherently difficult at scale. App developers need to create new features that users can use, which, in turn, helps the business make money. App developers also need to keep apps fast, consistent, fluid, fun, modular, and everything users expect from the app. A small app team can do both at once, but, as the team scales, focusing on these two things equally in a connected way is hard. Arnaud Lucas talks about this journey at Wayfair.