28/04/2023 11:16:00 AM (GMT)
NHSmail Reference : INC35555656
Microsoft Reference : MO547596
Issue Status : RESOLVED
Issue Description : MO545600 additional impact – Search queries may return partial results.
More Information : This notification concerns the remediation of persistent impact that resulted from the service impact described in MO545600.
Users running affected queries performed within customized or legacy versions of the search user interface (UI) within Microsoft 365 service platforms may have received an error when encountering this problem, although, users would not have seen an error when using the Modern Search UI.
Final Update : 16/05/2023 08:53:00 AM – Microsoft continued active monitoring for search performance issues during the weekend and beyond typical peak usage times. They have confirmed that the search service is performing at pre-incident functional levels or better. As such they are considering the issue to be resolved.
Scope of impact : This was a rarely occurring issue triggered by a user search query encountering search index error entries. Effectively, this issue impacted approximately one percent of customer users.
Root Cause : Impact described in MO545600 was caused by a service change that introduced an encoding mismatch between the crawler and query return service that serves Microsoft 365 service platforms. As a result of this mismatch, the service began writing incorrect entries into the search index that, when encountered, caused partial failures for user search queries and manifested as incomplete search results.