We've confirmed that all systems are back to normal with no customer impact as of 12/09, 18:34 UTC. Our logs show the incident started on 12/09, 17:27 UTC and that during the 1 hour and 7 minutes that it took to resolve the issue customers could have experienced missing alerts in West Europe.
Root Cause: The failure was due to a bad configuration
Incident Timeline: 1 Hour & 7 minutes - 12/09, 17:27 UTC through 12/09, 18:34 UTC
We understand that customers rely on Metric Alerts as a critical service and apologize for any impact this incident caused.
Update: Monday, 09 December 2019 18:08 UTC
Root cause has been isolated to a bad configuration which was impacting alerting. To address this issue we scaled out the deployment. Some customers may experience missing alerts in the West Europe Region.