Five Minute MongoDB - Change Streams and MongoDB 4.x` discusses the introduction of Change Streams in MongoDB 3.6, which simplifies listening to changes in a collection by providing a supported way to track updates. This allows for reactive programming and can be powerful in synchronizing different data services around MongoDB. The feature was improved upon with the addition of change streams on databases or entire deployments - replica sets or sharded clusters in MongoDB 4.0, enabling tracking of all changes across the database and deployment, including drop events when a collection is dropped, dropDatabase events when a database is dropped, and rename events when a collection is renamed. The feature provides real-time updates as the database and deployment change, making it easier to present MongoDB to another system in real-time.