Explore the concept of modular monoliths in this 47-minute conference talk from GOTO Berlin 2018. Dive into the principles of well-structured codebases, examining how to organize code based on technical and functional perspectives. Learn about package-by-layer and package-by-feature approaches, and understand the importance of aligning code structure with architectural intent. Discover how to apply component-based and service-oriented design thinking to monolithic codebases, emphasizing modularity, encapsulation, and boundary enforcement. Gain insights on using tools and techniques to maintain code quality, including static analysis and architecture violation checking. Understand the relationship between good architecture and agility, and learn to avoid common pitfalls such as the model-code gap. Whether you're working with monoliths or microservices, this talk provides valuable lessons on creating maintainable and scalable software architectures.