Invalidate Cloudfront's cached data by passing in custom header

Question

I need some resources or general direction.

I am looking into using Cloudfront to help combat latency on calls to my service.

I want to be able to serve cached data, but need to allow the client to be able to specify when they want to bypass cached data and get the latest data instead.

I know that I can send a random value in the query parameter to invalidate the cache. But I want to be able to send a custom header that will do the same thing.

Ideally, I would like to use the Cloudfront that is created behind the scenes with API Gateway. Is this possible? Or would I need to create a new CloudFront to sit in front of API Gateway?

Has anyone done this? Are there any resources you can point me to?

Answer 1

You cannot actually invalidate the CloudFront cache by passing a specific header -- or with a query parameter, for that matter. That is cache busting, and not invalidation.

You can configure CloudFront to include the value of a specific header in the cache key, simply by whitelisting that header for forwarding to the origin -- even if the origin ignores it.

http://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/distribution-web-values-specify.html#DownloadDistValuesForwardHeaders

However... the need to give your APIs consumers a way to bypass your cache seems like there's a problem with your design. Use an adaptive Cache-Control response header and cache the responses in CloudFront for an appropriate amount of time, and this issue goes away.

Otherwise, the clever ones will just bypass it all the time, by continually changing that value.