If you are on a paid Event Search plan, you can check your API usage.
To check your API usage, follow these steps:
You will be able to view a graph that shows your usage in your current period and for your previous period.
You will also be able to view a progress bar that shows your percentage of your request quota used.
If you use up your monthly requests, no worries. You'll simply go into overage charges at $3 per additional 1k requests (rounded up to nearest 1k) on any Event Search plan.
Your monthly invoice will also show your total usage including any overages.
NB: No graph will be shown if you're on a Data Licence as there is no limit on your usage.