This is a low-impact bug that only affects legacy/viewful timeseries.

Summary

SERVER-90889 implemented an inconsistency in checkMetadataConsistency if a timeseries system.buckets collection without a corresponding timeseries view is found.

During the commit of timeseries $out, we rename the temporary $out collection to "system.buckets.result" then create the timeseries view as two separate steps. If a checkMetadataConsistency comes in between those two steps, a false positive spurious MalformedTimeseriesBucketsCollection is reported.

On other DDLs like createCollection, this is prevented by the DDL lock, but $out does not hold it during the commit phase.

Proposed fix

We may ignore this issue since it's low impact and it is fixed with viewless timeseries.

A potential fix approach could be to verify if there is a temporary collection registered in "config.agg_temp_collections" and if so, discard the inconsistency.