Yes, circle provides the build container and docker, and our scripts install gcloud and kubectl and authorize a service account that can push to the associated project image repository.

Gotcha. We're doing the same thing here. The only problem is that Circle doesn't cache the image layers, so we do a full build every time, which takes about 10 minutes.

Yep same here, that's one of the things we need to improve on to get our deploy times down.