MigrationDestinationManager::cloneCollectionIndexesAndOptions takes a database MODE_X lock if the collection does not exist or is missing required indexes. This can cause stalls on transactions that involve other collections from the same database. This DB-level MODE_X lock seems excessive: Collection creation only needs collection/db in MODE_IX; and createIndexesOnEmptyCollection needs collection in MODE_X (so DB in MODE_IX).
This ticket is to consider relaxing at least the db-level exclusive lock to IX.