To communicate to the CK web service when a shoe's inventory has changed, an app builder should use an after-save record-triggered flow. An after-save record-triggered flow is a type of flow that runs after a record is saved and can perform actions such as updating related records, sending emails, calling external services, etc. An after-save record-triggered flow can use an Apex action to invoke a SOAP web service using a WSDL file. [Source]