There is still so much that you can learn when it comes to Cosmos DB and ASP.NET Core MVC. A single chapter is certainly not enough to cover it all. The days where databases sit on powerful, expensive servers that are housed in a rack in the office that only one guy has the keys to are very much numbered. This can be seen as good and bad: no-one can accidentally unplug or reboot the server, nor will a local power outage have any effect on it; however, you (or your employer) now pay for inefficient queries in pounds and pence (or dollars and cents).
In the next chapter, we will take a look at SignalR on Azure and how to create a real-time chat application.