Managing configuration and sensitive data through environment variables is essential for secure and flexible Node.js applications across different deployment environments. As the creator of CoreUI, a widely used open-source UI library, I’ve implemented environment variable management in numerous Node.js backend services for API keys, database connections, and deployment-specific configurations. From my expertise, the most secure approach is to use process.env with the dotenv package for local development. This method keeps sensitive data out of source code while providing easy configuration management across development, staging, and production environments.