We've confirmed that all systems are back to normal with no customer impact as of 04/22, 17:01 UTC. Our logs show that the incident started on 04/22, 16:11 UTC and that during the 50 minutes that it took to resolve the issue some of the customers might have experienced data access issues and delayed or missed Log Search Alerts in East US region.
Root Cause: The failure was due to an issue in one of our backend services.
Incident Timeline: 50 minutes - 04/22, 16:11 UTC through 04/22, 17:01 UTC
We understand that customers rely on Azure Log Analytics as a critical service and apologize for any impact this incident caused.