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.
When creating an API, you can select multiple entries from the list of default tiers. Also, you can add your own tiers to the API Manager using the instructions in section Adding New Throttling Tiers. At subscription time, the consumers of the API can choose which tier they are interested in. Accordingly, the subscriber is granted a maximum number of requests as defined in the tier s/he selected.
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.