Throttling is enabled in API Manager in different levels as follows:
An API can be available to a consumer at different levels of service. This is facilitated by throttling tiers. Throttling tiers are used to limit the number of hits to an API during a given period of time, typically in cases of infrastructure limitations, security concerns (preventing DOS attacks), monetization purposes etc.
Throttling can also be set at the application-level using the API Store. You can find more information on Application-Level Throttling.
Go back to Tier Availability section in Creating an API page.