For example, consider a course enrollment process where each student selects courses for that semester and then must pay for tuition. After enrolling in courses, a Task presents the student with a final invoice and payment options. When the student submits payment, the Request invokes a payment service's Application Program Interface (API), such as Stripe, to verify the payment. Use a Data Connector connector callback to monitor when the payment service's API verifies the payment information entered by the student. The Request now waits for a response from the payment service's API. The API response returns to a Request variable which can be used to determine next steps in that Request. If the student entered correct payment information and payment is honored, then their course enrollment is confirmed; otherwise the student must re-enter their payment details.