The Premium API: Application Hosting upgrade provides access to APIs with limited API calls.
If your mobile or web application exceeds the API limit your service will continue as normal up until 1.5x your capacity, so it's important to increase your limits promptly if you are expecting high traffic. If you exceed 1.5x capacity the API will automatically shut down for the remainder of the month, or until you upgrade.
How to check your allocated capacity and usage:
Login to Capitan and to to "Settings", you will find your license usage and capacity on the right hand side of the page.