Add a note about persistent images for auto devops deployments

doc/topics/autodevops/index.md

@@ -309,6 +309,18 @@ enable them.
 You can make use of [environment variables](#helm-chart-variables) to automatically
 scale your pod replicas.
 
+It's important to note that when a project is deployed to a Kubernetes cluster,
+it relies on a Docker image that has been pushed to the
+[GitLab Container Registry](../../user/project/container_registry.md). Kubernetes
+fetches this image and uses it to run the application. If the project is public,
+the image can be accessed by Kubernetes without any authentication, allowing us
+to have deployments more usable. If the project is private/internal, the
+Registry requires credentials to pull the image. Currently, this is addressed
+by providing `CI_JOB_TOKEN` as the password that can be used, but this token will
+no longer be valid as soon as the deployment job finishes. This means that
+Kubernetes can run the application, but in case it should be restarted or
+executed somewhere else, it cannot be accessed again.
+
 ### Auto Monitoring
 
 NOTE: **Note:**