Summary

In this chapter, you learned about the most important features that were added to MongoDB version 4. These were broken down into three categories: new features, security enhancements, and things to avoid during an upgrade from MongoDB 3 to 4. 

One important new feature was adding timestamps to the WiredTiger storage engine, which opened the doors for multidocument transaction support and nonblocking secondary read enhancements. Other internal enhancements include improvements in the shard-migration process, which significantly cuts down the time required for this operation to complete.

In the realm of security, you learned about how SHA-256 support gives you greater security when communicating with the MongoDB database, and also with communications between servers within a replica set or sharded cluster. You also learned that TLS 1.0 support has been removed, and that the new default is TLS 1.1. MongoDB 4.x even provides support for the latest version of TLS, version 1.3, but only if the underlying operating system libraries provide support.

Finally, as the original MongoDB storage engine, MMAPv1, has been removed in favor of WiredTiger, if your original MongoDB 3 installation had data that used MMAPv1, you need to back up while still running MongoDB 3 and then restore after the MongoDB 4.x upgrade has occurred. You were also presented with a list of the most significant items, including binary executables, parameters, and commands, which have been removed, and those which have been deprecated.

In the next chapter, you learn how to install MongoDB 4.x and its Python programming language driver.