While using sqlalchemy_enum34 I've seen the following error message:
SAWarning: TypeDecorator Enum('CREATED', 'RETRY', 'EXPIRED', 'FINISHED') will not produce a cache key because the cache_ok attribute is not set to True. This can have significant performance implications including some performance degradations in comparison to prior SQLAlchemy versions. Set this attribute to True if this type object's state is safe to use in a cache key, or False to disable this warning. (Background on this error at: https://sqlalche.me/e/14/cprf)
Apparently, only adding cache_ok = True would solve the problem.