Callout Quota System

Authorized Buyers Real Time Bidding system enforces a limit on the maximal rate of callouts (expressed in Queries Per Second, QPS) that can be sent to a bidder's servers. Pretargeting matches that exceed the limit are dropped. The limit:

  • Protects bidders from receiving more requests than their servers can handle.
  • Conserves Authorized Buyers resources when it knows that the bidder is not interested in receiving all eligible callouts (for example, the bidder is in test mode).

Quota limit

The limit is configured and enforced per bidder server URL (technically per trading location-URL pair, but bidders should not use the same server URL in multiple trading locations). The limit can be configured by the TAM or by the bidder through the Authorized Buyers API.

When you change the limit via the API, the total quota (for the account's all URLs) is disallowed to exceed the total quota configured internally by the TAM.

The maximum quota limit for your bidder also depends on your recent spend. Your effective quota limit before error throttling is the minimum of the configured quota and spend-based quota. You can view your spend-based quota on the RTB Graphs dashboard.

The Callout Quota System is strict (observed callouts should never exceed the limit), which makes it inaccurate at low volumes. This is more pronounced when the quota is small (less than 10 kQPS), which you can work around by setting the nominal quota limit higher than the intended effective one (for example, setting the quota limit to 1,500 QPS to get 1,000 QPS callouts).

Error throttling

The Callout Quota System uses error throttling—it sends less callouts than it can if the bidder does not respond to bid requests in time or if the bidder's responses are invalid. Note that error throttling:

  • Is triggered when more than 15% of the responses are invalid or timed out. If triggered, it will decrease the amount of callouts until either the error rate is less than 15%, or the number of bid requests goes down to some minimal amount of callouts.

  • Is applied in addition to and independently of the quota enforcement. Increasing the configured quota will have no effect on error throttling, which only cares about the error rate.

  • Adjusts within minutes to changing error rates.

Efficient callouts

Efficient callouts learn from historical bidding behavior, but use more revenue-sensitive criteria: whether bidders bid above reserve prices, not just whether they bid or not. Efficient callouts also use fewer dimensions for segmentation to avoid overfitting.

For example, imagine a scenario where a bidder is subject to a quota constraint of 100 queries. If there are 1000 potential queries available, and if there's no quota constraint, the bidder will bid on 500 queries and bid above reserve on 200 queries. The following table shows the result for different filtering models.

Total queries Efficient callout filtering Random quota throttling Maximum queries the bidder can win
1000 -900 20
1000 -400 40
1000 -300 -100 100

Randomly dropping queries to satisfy quota constraint ignores bidding behavior and results in the fewest number of queries that bidders can win. Applying efficient callouts filters out queries on which a bidder can bid but is not likely to win, and provides the maximum number of winnable queries.

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