Rule-based architectural patterns produce solutions that are highly performant, composable, loosely coupled, flexible, and can be thoroughly tested. A rule-based approach to application logic integrates well with other architectural patterns such as big data analysis output, streaming data pipelines for real-time processing, or message-oriented processing. Rule-based architectures complement microservices architectures too. Large unwieldy opaque rule engines of the past are not required. Nor are rule-specialized languages and tooling. Developers don’t need specialized training when rules are implemented with the language of the project, available collections API, and business domain language. This session describes an internal architectural pattern to implement complex business logic to deliver quality software that endures. The concepts can be implemented in any language.