MongoDB Documentation, Release 3.0.4 db.categories.find( { children: "MongoDB" } ) The Child References pattern provides a suitable solution to tree storage as long as no operations on subtrees are necessary. This pattern may also provide a suitable solution for storing graphs where a node may have multiple parents. Data in MongoDB has a flexible schema . Collections do not enforce document structure. Decisions that affect how you model data can affect application performance and database capacity. See Data Modeling Concepts (page 145) for a full high level overview of data modeling in MongoDB. This document describes a data model that describes a tree-like structure in MongoDB documents using references (page 147) to parent nodes and an array that stores all ancestors. The Array of Ancestors pattern stores each tree node in a document; in addition to the tree node, document stores in an array the id(s) of the node’s ancestors or path. Consider the following hierarchy of categories: Model Tree Structures with an Array of Ancestors Overview Pattern Chapter 4. Data Models 160