Does Azure front door actively replicate its cache?

Question

Does the AFD cache push / replicate out to additional POP's, once an initial request to a single POP has completed? I cant find any documentation on the AFD documentation in relation to this.

Ultimately what I want to know is:

If an initial request occurs from EU, served by the EU POP (after pull though from origin server); then 1h later an identical request occurs from the US, is this request a 'cache hit' in the US POP, or a miss with a read through?

Answer 1

The first request by the any POP will not be cached. As per your example, the request sent form US will be a MISS and any subsequent request will be cached in that POP server.

Answer 2

We were seeing mixed behaviour on our systems, and the below extract explains how AFD functions, and why we got the mixed behaviour.

Lets say out of out of 100 POPs globally, we have 20 super POPs. The remaining 80 will never reach the API backend directly but will only go to super POPs. And then the Super POPs go to your API to pull the content. There on not just the initial POP but also the super POP now have the cached content. Across the globe the Super POPs keep getting warmed up with the cache content. Each Edge POP has a mapping to a Super POP. This overall helps improve cache hit ration significantly and also significantly reduces the load on your application backends.