Modularisation is a demanding topic. With modularisation, you can have extraordinary achievements or spectacular failures. We split 200k lines of monolith app modules into 150+ modules with 10+ developers. Now we can contribute faster, test features in isolation and use foundation modules for best practices. With an increasing number of features and code, we needed a scalable codebase. During the process, we find out practical patterns, and we had lots of pitfalls. In the end, improved build speed, uncoupled features, strong foundation for best practices come with modularisation. Separated responsibility layers help team members contribute and contain changes in smaller efforts. Correct modularisation is the foundation of having scalable codebases. From navigation to reusing views and resources, your mental model needs to change. In this talk, you will learn compelling problems you can encounter and how to overcome issues proficiently.