Currently, the DurableCatalogImpl::_idents map is keyed by namespace. When creating a duplicate collection with the same namespace, the catalog will return a namespace already exists error.

That error acts as an "early write conflict"; if everything else in the system allowed concurrent collection creation on the same namespace (where of course only one transaction can win committing), that collection management would be a serialization point.

The consensus change is to instead keep the map, but index that data by the RecordId in the durable _mdb_catalog table. Collections and/or RecordStores will hold onto their RecordIds.