Absence of architecture to describe how to implement authorization as a centralized service, in a way similar to authentication, has been causing redundant deployment of computing resources, lack of standard practices, and never-ending learning curve in maintaining proprietary or ad hoc authorization solutions. The paper develops an architecture, which focuses on centralization of authorization, to be called Centralized Authorization Service (CAuthS) or Authorization-as-a-Service (AuthaaS), when deployed as a service, and is targeted to substitute platform-based ad hoc authorization solutions.