November 2021
12
Summary of Impact: Between 02:00 UTC on 12 Nov 2021 and 17:00 UTC on 15 Nov 2021, a subset of customers primarily located in the North America and APAC geographies may have encountered intermittent 400-level errors when attempting to access Microsoft Graph APIs.
Preliminary Root Cause: We determined that a recent update to improve the underlying Microsoft Graph API infrastructure created a configuration issue between the Microsoft Graph API interface and its underlying Internet Information Services driver. This configuration issue prevented calls to various APIs from completing as expected.
Mitigation: We failed-over our service to a previously-known healthy state and rolled back the update to mitigate impact.
Next steps: We sincerely apologize for the impact to affected customers. We will continue to investigate to establish the full root cause and prevent future occurrences. Stay informed about Azure service issues by creating custom service health alerts: https://aka.ms/ash-videos for video tutorials and https://aka.ms/ash-alerts for how-to documentation.