It would be interesting to see a comparison to App Engine, which seems like a better fit than Kubernetes for low-traffic sites.
Cloud Run would be the slightly more general and newer way to do this too, and the free tire there is 2 million req/month. I _think_ he could have migrated containers directly from GKE.
See GCP calculator: https://cloud.google.com/products/calculator/#id=36a5f437-98...