api-management-cache-example-policy-expressions.md

author	dlepow
ms.service	azure-api-management
ms.topic	include
ms.date	11/24/2025
ms.author	danlep

Example using policy expressions

This example shows how to configure API Management response caching duration that matches the response caching of the backend service as specified by the backend service's Cache-Control directive.

<!-- The following cache policy snippets demonstrate how to control API Management response cache duration with Cache-Control headers sent by the backend service. -->

<!-- Copy this snippet into the inbound section -->
<cache-lookup vary-by-developer="false" vary-by-developer-groups="false" downstream-caching-type="public" must-revalidate="true" >
  <vary-by-header>Accept</vary-by-header>
  <vary-by-header>Accept-Charset</vary-by-header>
</cache-lookup>
 <rate-limit calls="10" renewal-period="60" />

<!-- Copy this snippet into the outbound section. Note that cache duration is set to the max-age value provided in the Cache-Control header received from the backend service or to the default value of 5 min if none is found  -->
<cache-store duration="@{
    var header = context.Response.Headers.GetValueOrDefault("Cache-Control","");        
    var maxAge = Regex.Match(header, "@(max-age=(?<maxAge>\\d+))").Groups["maxAge"]?.Value;
    return (!string.IsNullOrEmpty(maxAge))?int.Parse(maxAge):300; }" />

For more information, see Policy expressions and Context variable.