I recently experienced slow down with
docker build, after I ran
gcloud auth configure-docker.
The 10 seconds slow down is caused by the extra step of
gcloud authentication, even though you are not using the
gcr.io registry in your current build.
To solve this problem, just rename the file under
~/.docker/config.json to something else, like:
mv ~/.docker/config.json ~/.docker/config.json.gcloud