Query Analysis

In order to write efficient queries, it is important to analyze them, find any possible performance issues, and fix them. This technique is called performance optimization. There are many factors that can negatively affect the performance of a query, such as incorrect scaling, incorrectly structured collections, and inadequate resources such as RAM and CPU. However, the biggest and most common factor is the difference between the number of records scanned and the number of records returned during the query execution. The greater the difference is, the slower the query will be. Thankfully, in MongoDB, this factor is the easiest to address and is done using indexes.

Creating and using indexes on a collection narrows down the number of records being scanned and improves the query performance noticeably. Before we delve further into indexes, though, we first need to cover the details of query execution.

Say you want to find a list of the movies released in the...