Config as Code allows you to specify service build and deploy settings in a file alongside your code, which can be a railway.toml or railway.json file by default or a custom file specified in the service settings. This approach brings the power of git to your service build and deploy configuration, allowing for version control, rollback, and easy management of different environments with similar configurations. It also enables custom start commands per environment, separate config per environment, and reproducibility for shared projects. By using Config as Code, you can incorporate settings at your own convenience and track them in Git, ensuring determinism for your collaborators.