Side-by-side extensibility is the type of extensibility where the SAP Business Technology Platform is used to host a custom extension and integrate it with the SAP S/4HANA Cloud system. Side-by-side extensibility enables customers and partners to build extensions that are decoupled from the core SAP S/4HANA Cloud system, ensuring lifecycle stability and avoiding modification of SAP code. Side-by-side extensibility leverages the capabilities of the SAP Business Technology Platform, such as SAP Cloud Platform Workflow Services, SAP Cloud Platform Business Rules, SAP Cloud Platform Integration, and SAP Cloud Platform Extension Factory. References = Utilizing the Clean Core Strategy and Extensibility Tools; Using Side-by-Side Extensibility with SAP Business Technology Platform