Separating environment variables and infrastructure modules into dedicated repositories offers significant benefits in terms of security, scalability, and maintainability, as demonstrated by Acme Corp's experience during their cloud migration. By isolating these elements, organizations can implement granular access control for sensitive information, maintain independent versioning and release cycles for modules, and streamline collaboration across teams, resulting in a reduction of security incidents and faster deployment times. Implementing best practices, such as robust version control, comprehensive testing strategies, and strict access control measures, is essential for managing infrastructure code effectively at scale. Tools like Harness facilitate these practices by providing features for securely managing environment variables and module registries, ultimately supporting the creation of a scalable, secure, and maintainable infrastructure codebase.