I struggled recently getting AWS Gateway to implement query string caching. Here is the order of the steps you need to take:

1. In the API Gateway console, under Resources, navigate to your API method and method.
2. In Method Request, add a new URL Query String parameter checking Required and Caching.

3. Deploy the API (because you always forget!)
4. Under Stages, on the Settings tab, click the Enable API cache API.

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