builder.Dockerfile defines a container with all of the required dependencies to build the site + documentation. In order to speed up the deployment, an image of this container is deployed to the Google Container Registry (GCR) (gcr.io/gold-hybrid-255313/builder). This image is used to spawn a Gcloud ‘Cloud Build’ job whenever a PR is merged into master, which runs the steps in cloudbuild-deploy-docs.yaml. After running the site build script (util/site/build-docs.sh), this job copies the generated artifacts to the Gcloud bucket which serves the website. This cuts the deployment of any updated site/documentation changes down to about 1 minute.