By default, if your app executes more than 30 API calls over 10 seconds, your app will be throttled, and you should retry the call later. You will receive the following error response:
Our goal with throttling is that any API application under normal circumstances will never be throttled. Throttling is in place to protect API partners and WePay from A) attacks and B) programming errors in an app that can cause API calls on infinite loops. Please let us know if you anticipate a high API call volume and want the default throttle limits raised for your app.