I sometimes wonder about all the additional HTTP load to places like debian.org that must come from Docker builds; I don't have any kind of caching in mine, and

I sometimes wonder about all the additional HTTP load to places like debian.org that must come from Docker builds; I don't have any kind of caching in mine, and every single commit causes CI to go and build images and run tests on them. It's not an issue I really see, but it seems to me that CI infrastructure (Travis, ...) really should have caching proxies in place.