Please also see this recent thread, as it’s relevant to this part of the system: 500 errors accessing an older course in our LMS, modulestore values out of sync? - Development - Open edX discussions
That being said, this is a very low-level representation of the content data. Depending on your use case, you might be better off using the Course Blocks API or doing queries in modulestore. Our longer term goal is to get rid of MongoDB from the system and to change how we store this content on the backend.