# PrefetchRetrieval
<a name="API_PrefetchRetrieval"></a>

A complex type that contains settings governing when MediaTailor prefetches ads, and which dynamic variables that MediaTailor includes in the request to the ad decision server.

## Contents
<a name="API_PrefetchRetrieval_Contents"></a>

 ** EndTime **   <a name="mediatailor-Type-PrefetchRetrieval-EndTime"></a>
The time when prefetch retrieval ends for the ad break. Prefetching will be attempted for manifest requests that occur at or before this time.  
Type: Timestamp  
Required: Yes

 ** DynamicVariables **   <a name="mediatailor-Type-PrefetchRetrieval-DynamicVariables"></a>
The dynamic variables to use for substitution during prefetch requests to the ad decision server (ADS).  
You initially configure [dynamic variables](https://docs.aws.amazon.com/mediatailor/latest/ug/variables.html) for the ADS URL when you set up your playback configuration. When you specify `DynamicVariables` for prefetch retrieval, MediaTailor includes the dynamic variables in the request to the ADS.  
Type: String to string map  
Required: No

 ** StartTime **   <a name="mediatailor-Type-PrefetchRetrieval-StartTime"></a>
The time when prefetch retrievals can start for this break. Ad prefetching will be attempted for manifest requests that occur at or after this time. Defaults to the current time. If not specified, the prefetch retrieval starts as soon as possible.  
Type: Timestamp  
Required: No

 ** TrafficShapingRetrievalWindow **   <a name="mediatailor-Type-PrefetchRetrieval-TrafficShapingRetrievalWindow"></a>
Configuration for spreading ADS traffic across a set window instead of sending ADS requests for all sessions at the same time.  
Type: [TrafficShapingRetrievalWindow](API_TrafficShapingRetrievalWindow.md) object  
Required: No

 ** TrafficShapingType **   <a name="mediatailor-Type-PrefetchRetrieval-TrafficShapingType"></a>
Indicates if this configuration uses a retrieval window for traffic shaping and limiting the number of requests to the ADS at one time.  
Type: String  
Valid Values: `RETRIEVAL_WINDOW`   
Required: No

## See Also
<a name="API_PrefetchRetrieval_SeeAlso"></a>

For more information about using this API in one of the language-specific AWS SDKs, see the following:
+  [AWS SDK for C\$1\$1](https://docs.aws.amazon.com/goto/SdkForCpp/mediatailor-2018-04-23/PrefetchRetrieval) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/mediatailor-2018-04-23/PrefetchRetrieval) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/mediatailor-2018-04-23/PrefetchRetrieval)