A notification metric is cheap only when it can answer who created the work, which delivery stage failed, and who owns the retry. Choose the backend after fixing that attribution model. For a customer-support notification service, I would compare four paths with the same bounded dataset: CloudWatch, Grafana Cloud's free offering, PostHog, and a small self-hosted metrics API. The winner is the path whose total operational burden fits the team and whose labels preserve responsibility without expos...