Steps to reproduce:

1. Use Redis as a cache.
2. Add URL field of identifier url to Folder Content Type.
3. Copy and paste the attached command file in the src/Command directory.
4. Run the command with: php bin/console app:create-content.
5. Observe the logs and/or terminal output.

Result:
You will start seeing the following exceptions:

14:56:11 CRITICAL  [app] An exception occurred while executing 'INSERT INTO `ezurl_object_link` (contentobject_attribute_id, contentobject_attribute_version, url_id) VALUES(?, ?, ?)' with params [12764, 1, "92"]:

SQLSTATE[40001]: Serialization failure: 1213 Deadlock found when trying to get lock; try restarting transaction

Some of the contents were not created (5 processes * 100 iterations = 500 contents) in the root folder.

Expected result:
No exceptions. You should see 500 contents created.

Note:
Increasing the number of parallel processes will result in more exceptions.