When a write is targeted, the router ensures the target database is created by using the cluster DDL API. However, if the database is subsequently dropped before the collection refresh in the insert path, the operation fails with NamespaceNotFound error.

A variant of this problem was already fixed in the context of SERVER-83146. However, there are multiple scenarios where the problem can still occur. The management of the time-series collections required multiple paths that must be reviewed in the context of this fix.

The probability of the problem occurring in a real-world scenario is negligible. The cost of the fix is a couple of days at most.