The last thing we want to discuss when it comes to custom Elasticsearch plugins is the analysis process extension. We've chosen to show how to develop a custom analysis plugin because this is sometimes very useful, for example, when you want to have the custom analysis process that you use in your company introduced, or when you want to use the Lucene analyzer or filter that is not present in Elasticsearch itself or as a plugin for it. Because creating an analysis extension is more complicated compared to what we've seen when developing a custom REST action, we decided to leave it until the end of the chapter.