We covered a lot of ground in this chapter. In the beginning, you saw Couchbase only as a key/value store. Since then, you learned that Couchbase is a very capable document store as well, treating JSON documents as first-class citizens.

You learned the purpose of secondary indexes in a key/value store. We dug deep into MapReduce, both in terms of its history in functional languages and as a tool for NoSQL and big data systems.

As far as Couchbase MapReduce is concerned, we only scratched the surface. While you learned how to develop, test, and query views, the queries covered so far were simple. Couchbase view queries are capable of a lot more, which you will see as we move forward.

In the next chapter, we'll cover MapReduce in detail. We will have to start exploring more complex views, with a special focus on queries you're probably used to in SQL. From complex keys to simulating joins, you'll soon see that Couchbase views can be used for a lot more than simple queries.