Identify GPII application events that need to be tracked, their normal/abnormal levels, etc.
Components such as the Preferences Server, Flow Manager, etc. could make use of this project https://github.com/prometheus/pushgateway#command-line or an unofficial Node.js client https://github.com/siimon/prom-client
Configure clients to send data and server to store/display/report on it.
Define initial operational thresholds for normal, warning and critical levels.
Define alerts in Prometheus.
Annotate events so that context is available when viewing metrics/alerts. Aid in troubleshooting.