I don’t know why in the tree pattern’s lab the best option is not child references.
I mean, we want to know all the direct reports of an employee efficiently. This is the best option because we have all the people that report to us only accesing to a document, avoiding mongoDb accesing other documents and indexes.
Also, we could know who is our manager, altough it is more complicated query (but the problem didn’t have a constraint about it).
Can you explain me better? Thank you.