Feature flags are configuration variables used to enable or disable features in an application. They allow mobile engineering teams to deploy new features instantly without going through the app store, reducing the risk of introducing bugs and ensuring that users can test new features safely. Feature flags can be used for various scenarios such as product and marketing campaigns, A/B testing, subscription management, and opt-in early access campaigns. However, their use can also lead to increased technical debt, code complexity, and testing complexity if not managed properly. To optimize mobile deployments with feature flags, it's essential to establish best practices, such as using a sensible naming convention, controlling access, and limiting the life span of feature flags. Various implementation paths exist, including config files, database configs, open-source libraries, and third-party services.