The amp.yml file deploys every component of 3scale. According to the 12 factors best practices, backing services dependencies are referenced through Environment Variables, which is perfect.

Except for system-memcache that is hardcoded in a cache_store.yml file in the system image !

It would be better if the cache_store.yml were generated as a configMap and not hardcoded.
It would be even better to accept environment variables which are easier to use (the underlying cache library, dalli, supports it) !