Oracle APEX architecture
Oracle APEX uses a database encapsulated simple metadata-driven architecture that provides fast data access, top performance, and scalability, out of the box.
Oracle APEX uses a simple 3-tier architecture where requests are sent from the browser, through a web server, to the database. All processing, data manipulation and business logic is executed in the database. This architecture guarantees zero latency data access, top performance, and scalability, out of the box.
A web request from the web browser is sent to Oracle REST Data Services (ORDS) where it is handed to Oracle Database to be actioned. Within the database, the request is processed by Oracle APEX. Once the processing is complete, the result is sent back through ORDS to the browser. https://apex.oracle.com/en/platform/