Changed the color to #ead746 and deployed, ready to merge
We have performed the migration, downtime was only a few seconds. We have also tried a running update for a non existing Docker image tag. The new pod kept running, a new one was created and failed to pull the image; I reverted the Docker image to the 1.9.0 tag and the failed pod was deleting, leaving the previous one.
It turns out we can get rid of one of the 3 small nodes after all. The master is managed by GKE (https://cloud.google.com/kubernetes-engine/docs/concepts/cluster-architecture#master). The minimum of 3 nodes in a cluster is when you run your own cluster, because etcd needs at least 3 nodes for a production cluster; this is what the Kubernetes docs and blog posts are talking about, not the case of a managed service like Amazon EKS or GKE. This is confusing because they are still "nodes", but they don't have a role and only run pods, they do not provide the actual Kubernetes API (the master managed by GKE does)