We've confirmed that all systems are back to normal with no customer impact as of 08/16 00:00 UTC. Our logs show the incident started on 08/15 16:00 UTC and that during the 8 hours that it took to resolve the issue customers who had workspaces in East US would have experienced data access issues in Log Analytics portal.
Root Cause: The failure was due to issues with one of the backend service.
Incident Timeline: 8 Hours - 08/15 16:00 UTC through 08/16 00:00 UTC
We understand that customers rely on Azure Log Analytics as a critical service and apologize for any impact this incident caused.