Mastering monorepo management is vital for large codebases: this guide compares Nx's flexible, plugin-based framework with Lerna's zero-config simplicity, explains when to choose each (Nx for complex, highly customized repos; Lerna for smaller, speed-focused setups), outlines core skills (JavaScript, package managers, build tools, Git), and illustrates benefits via a fintech use case to boost scalability, efficiency, and maintainability.