What type of NoSQL database is best suited to store hierarchical data?

Question

What type of NoSQL database is best suited to store hierarchical data?

Say for example I want to store posts of a forum with a tree structure:

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Answer 1

In mathematics, and, more specifically, in graph theory, a tree is an undirected graph in which any two vertices are connected by exactly one path. So any graph db will do the job for sure. BTW an ordinary graph like a tree can be simply mapped to any relational or non-relational DB. To store hierarchical data into a relational db take a look at this awesome presentation by Bill Karwin. There are also ORMs with facilities to store trees. For example TypeORM supports the Adjacency list and Closure table patterns for storing hierarchical structures.

TypeORM is used in TypeScript\Javascript development. Check popular ORMs to find a one supporting trees based on your environment.

The king of Non-relational DBs [IMHO] is Mongodb. Check out it's documentation. to find out how it stores trees. Trees are the most common kind of graphs and they are used everywhere. Any well-established DB solution should have a way to deal with trees.