In this chapter we've looked at cluster health and state monitoring both by using the ElasticSearch API and by using various tools. In addition to that we've learned how to control shard and replica allocation. We've also seen how to use the gateway module to store indices and their metadata, and we've learned what a discovery module is responsible for and how to configure it. Finally we've seen how to install third-party plugins for ElasticSearch. In the next chapter, we will discuss how some common problems can be overcome; for example, we'll see how to scroll through a large number of search results, how to validate your queries, and how to use the query warm up functionality. We'll also see how to control cluster rebalancing.