Microsoft service issue causing 503 ‘Service Unavailable’ responses from SharePoint API

Incident Summary: We are currently observing an elevated rate of 503 'Service Unavailable' responses impacting CDM. Microsoft have confirmed that this is not expected behaviour and forms part of an ongoing investigation within the Microsoft Commercial Cloud service. Root cause is attributed to Microsoft service-side. IAM Cloud Services Affected: Cloud Drive Mapper, v3.x versions Current Impact: Multiple customers are experiencing repeated 503 responses leading to performance degradation. The issue is being experienced globally, although not consistently across all tenancies. It is important to note that this issue is distinct from throttling. Microsoft have confirmed that throttling mechanics have not changed and that excessive calls to MS Graph will still generate 429 ‘Too Many Requests’ responses prior to 503 ‘Service Unavailable’ errors being generated. For users impacted by the current issue, there are no 429 errors returned, and our investigations show that tenancy-level MS traffic limits are not being exceeded. The 503s are unexpected and are abnormal. Resolution Status: We have escalated the issue with Microsoft to the highest possible level based on customer impact. Microsoft has acknowledged the issue and confirmed an active investigation. No estimated time for resolution has been provided. Recommended Action: Please contact our Support Desk if you are being impacted by this issue. We encourage customers to raise support requests direct with Microsoft to ensure their tenant impact is captured as part of the ongoing investigation. When contacting Microsoft Support, we recommend referencing the ‘ongoing internal Microsoft Engineering team investigation into an unexpected increase in 503 responses in SharePoint Online calls in Commercial Cloud beginning in the last week of February’. Fix ETA: As yet Microsoft have not provided a fix ETA. Next update: We are continuing to monitor the situation closely and will provide updates as Microsoft shares further information.