With Marek, we were thinking about writing an update to Mastering Elasticsearch, Packt Publishing. It was not a book for everyone, but the first version didn't put enough emphasis on that—we were treating Mastering Elasticsearch as an update to Elasticsearch Server. The same goes with Mastering Elasticsearch Second Edition. The book you are holding in your hands was written as an extension to Elasticsearch Server Second Edition, Packt Publishing, and should be treated as a continuation to that book. Because of such an approach, we could concentrate on topics such as choosing the right queries, scaling Elasticsearch, extensive scoring descriptions with examples, internals of filtering, new aggregations, comparison to documents' relations handling, and so on. Hopefully, after reading this book, you'll be able to easily get all the details about Elasticsearch and the underlying Apache Lucene architecture; this will let you get the desired knowledge easier and faster.

I would like to thank my family for the support and patience during all those days and evenings when I was sitting in front of a screen instead of being with them.

I would also like to thank all the people I'm working with at Sematext, especially Otis, who took his time and convinced me that Sematext is the right company for me.

Finally, I would like to thank all the people involved in creating, developing, and maintaining Elasticsearch and Lucene projects for their work and passion. Without them, this book wouldn't have been written and open source search wouldn't have been the same as it is today.

Once again, thank you.