In this chapter, we were focused on the performance and scaling of Elasticsearch. We looked at how doc values can help us with improving the query performance, how garbage collector works, and what to look at when changing its configuration. We benchmarked our queries and we saw what the Hot Threads API is. Finally, we discussed how to scale Elasticsearch and how to prepare it for high querying and indexing use cases.

In the next chapter, we will write some code. We will create the Apache Maven project used to write Elasticsearch plugins. We will write a custom REST action to extend the Elasticsearch functionality. In addition to this, we will learn what needs to be done in order to introduce new analysis plugins for Elasticsearch, and we will create such plugins.