Microsoft Azure API Management - Cache policy doesn't work

Question

I have tried to set a caching policy in Azure API Management as follows:

<policies>
    <inbound>
        <base />
        <cache-lookup vary-by-developer="false" vary-by-developer-groups="false" must-revalidate="true" downstream-caching-type="none" caching-type="internal">
            <vary-by-query-parameter>KontoNr</vary-by-query-parameter>
        </cache-lookup>
        <set-backend-service id="apim-generated-policy" backend-id="LogicApp_GeldEinzahlen_APIM_f597e3433e7847cb9d689c3f95bf1d6d" />
        <validate-jwt header-name="Authorization" failed-validation-httpcode="401" failed-validation-error-message="Unauthorized. Access token is missing or invalid.">
            <openid-config url="https://login.microsoftonline.com/1b7c4ba5-7701-49e7-94d8-5ddbc87f8b6e/v2.0/.well-known/openid-configuration" />
            <required-claims>
                <claim name="aud">
                    <value>7068cdb6-0e5c-49c5-aaa8-ec8fc941de22</value>
                </claim>
            </required-claims>
        </validate-jwt>
        <set-variable name="isKontoNr" value="@(context.Request.MatchedParameters["kontoNr"].ToString().Length != 10)" />
        <choose>
            <when condition="@(context.Variables.GetValueOrDefault<bool>("isKontoNr"))">
                <return-response>
                    <set-status code="400" reason="Bad Request" />
                    <set-header name="WWW-Request" exists-action="override">
                        <value>Generell error="kontoNr invalid"</value>
                    </set-header>
                </return-response>
            </when>
        </choose>
    </inbound>
    <backend>
        <base />
    </backend>
    <outbound>
        <base />
        <cache-store duration="1000" />
    </outbound>
    <on-error>
        <base />
    </on-error>
</policies>

I have pricing tier "Developer" so the internal cache has to be available but if i make a request i always get the following response:

HTTP/1.1 200 OK

cache-control: no-cache
content-encoding: gzip
content-type: text/plain; charset=utf-8
date: Tue, 12 Jan 2021 15:54:26 GMT
expires: -1
pragma: no-cache
strict-transport-security: max-age=31536000; includeSubDomains

cache-control is always 'no-cache' no matter what i send in the header.

How can i fix it? Is some other configuration needed or have i enable something?

Answer 1

As silent mentioned in comments, the message cache-control: no-cache should not really be indicative whether the cache was being used. The <cache-lookup> policy is correct in your APIM.

When you request the api(for test in APIM page) first time, click " Trace " --> " Inbound ". You can find the message Cache lookup resulted in a miss because there is no cache when you request first time.

And then click " Outbound ", you can find Response will be buffered during streaming and stored in the cache after it is received in full .

Then, since you specified the cache be stored for 1000 seconds, so if you request again in 1000 seconds, you can find the message Cache lookup resulted in a hit! under " Inbound ".

Please test in your side, and if the result is same with what I mentioned above, the policy <cache-lookup> works fine in your APIM.