Abstract: Some embodiments may be associated with a system to extend business logic for cloud application services. A custom logic user interface may receive, from a user via a flow-based editor, information creating a custom logic business expression (e.g., a determination or a validation) and information about the custom logic business expression may be stored in a custom logic metadata repository. A computer processor of an application service platform may access the custom logic business expression from the custom logic metadata repository and receive an Application Programming Interface (“API”) call from an API consumer. Responsive to the API call, the system may arrange for execution of the custom logic business expression in accordance with information in the custom logic metadata repository and invoke a pre-hook trigger event to call a custom logic service. Standard application logic may then be executed, and a post-hook trigger event may be invoked to call the custom logic service.