My main use case for Qlik Talend Cloud is often for creating REST services, SOAP services, and rarely for doing ETL.
Let's say we want to launch a project where the client has to go through a menu with options, then enter the amount, then enter the recipient's number for the credit or the bundle. On our side, we create a service that we expose and can call, for example, 'purchase bundle.' This 'purchase bundle' service will take as input the bundle ID and the recipient's number as a GET service. In the service flow, it will be a REST service which in the flow will first call a backend to check whether the initiator has sufficient credit, then a second backend to check whether the sender's number is a valid number, then a third backend to check whether this product is a valid product. After all these checks, it then gives the product to the recipient and returns a response. Since it's a GET service, the response could be in XML or JSON. In that response, there will be a 200 status code. Then, in the payload of the response, it will depend on what we want to give. We can for example put 'successful,' 'the request was processed successfully,' or just put 'OK.' In any case, it will be something where, when you see it, you'll know that this is a success.
Generally, that's it. I gave you a practical case. There are many cases and several cases, but in all cases, it revolves around REST or SOAP services.