In this article, the author discusses the importance of indexing in MongoDB for improving performance. Indexing allows the database to efficiently execute queries by limiting the number of documents that need to be inspected. The author provides best practices for creating and maintaining effective indexes in MongoDB, including using compound indexes, following the ESR rule, and utilizing query coverage. They also discuss common pitfalls, such as ignoring fields with low cardinality, and provide recommendations for optimizing performance. Additionally, the article touches on the use of full-text search, partial indexes, and index statistics to further improve performance.