In this chapter we went through advanced querying concepts using Ruby, Python, and PHP both using the official drivers and an ODM.

Using Ruby and the Mongoid ODM, Python and the PyMODM ODM, and PHP and the Doctrine ODM, we went through code samples exploring how to create, read, update, and delete documents. 

We also discussed batching operations for performance and best practices. We presented an exhaustive list of comparison and update operators that MongoDB uses.

Finally, we discussed smart querying, how cursors in querying work, what our storage performance considerations should be on delete, and how to use regular expressions.

In the next chapter we will learn about the aggregation framework, using a complete use case that involves processing transaction data from the Ethereum blockchain.