To ensure that Google sends you the most appropriate impression calls, you
can *pretarget* impressions to receive requests for only the impressions
that match your targeting criteria by using one of the following:

- [Authorized Buyers UI](https://support.google.com/authorizedbuyers/answer/6048315)
- [Real-time Bidding API](https://developers.google.com/authorized-buyers/apis/guides/rtb-api/pretargeting-overview)

## Quota management

The quota system manages quota by these four locations (see **Trading
Locations** under [Peering](https://developers.google.com/authorized-buyers/rtb/peer-guide#bidder-locations) for
details):

- North America (East Coast)
- North America (West Coast)
- Europe
- Asia Pacific

In each trading location you can define multiple bidding endpoints (up to
**8** ), each identified by a URL (for example,
`http://us-east.my_bidder.com:1234/google_rtb`) to which Authorized
Buyers sends bid requests. Each bidding endpoint has its own callout limit (in
callouts per second)---you can configure the endpoints and their limits by
contacting your technical account manager or through the [Buyer
API](https://developers.google.com/authorized-buyers/apis/reference/rest/v2beta1/accounts.clients/update).

The quota system guarantees that an endpoint does not get more callouts than
its callout limit. If in a trading location where there are less pretargeted
impressions than the total endpoint capacity, the quota system balances the
callouts among the endpoints. The quota system also implements error
throttling---if an endpoint has high callout error rate, the system
lightens its load by enforcing a stricter callout limit than the configured
one. If there is spare capacity in other endpoints in the same trading
location, error throttling will cause the callouts to shift to them; otherwise
the excess pretargeted impressions will be dropped.

Because quota management comes after pretargeting, it does not affect the
total number of pretargeted impressions in a trading location. It can only
shift callouts among endpoints in the same trading location, or drop excess
pretargeted impressions if the callout capacity is exhausted.