I have been testing several of the AMP Apps to get Accelerated Mobile Pages working on my site. Based on the URL's in question most of these Apps utilise the Shopify Proxy App to contact the Apps server in order to render product pages. From my location all of these Apps have an issue with very slow Time To First Byte, largely I beleive for 2 reasons.
1. The pages cache settings are set to re-validate, hence every refresh of the page requires contact back to the shopify servers, forwarded by the Shopify App proxy to the Apps Servers and returned with a HTML response code of 304.
2. The location of the Shopify Server I hit in Australia vs the location of the App servers location, notably in the United States causes a long round trip time resulting in slow Time To First Byte
So my question is this, can the Shopify App Proxy be told by the App servers to cache the information returned to it from the Apps servers so it does not require revalidation for every page request?
This phenomonon can be tested using Gtmetrix and setting the location used for testing. I have used both Vancouver and Sydney resulting in very different TTFB.
What has been the experience of other store owners with AMP Apps?