Which of the following is not a use case for the SOAP API?

The choice of "Stream live data" is not a use case for the SOAP API. The SOAP API is primarily designed for synchronous operations where a request is sent to the server, and a response is returned, making it well-suited for operations like creating, updating, or deleting records.

When it comes to functionalities such as creating new records or updating existing records, the SOAP API provides robust support for these CRUD (Create, Read, Update, Delete) operations. It allows developers to interact with Salesforce data in a structured manner, utilizing the rigid formatting of the SOAP protocol.

Processing approval workflows is also a valid use case because workflows can often involve creating or updating records and sending notifications, all of which is achievable through the SOAP API.

However, streaming live data is typically associated with event-driven architectures or services that provide real-time updates—such as the Streaming API in Salesforce—rather than the more transactional nature of the SOAP API. Therefore, "Stream live data" stands out as the incorrect choice for SOAP API use cases.