This is our third book on Elasticsearch and the second edition of the first book, which was published a little over a year ago. This is quite a short period but this is also the year when Elasticsearch changed. Not more than a year ago, we used Version 0.20; now, Version 1.0.1 has been released. This is not only a number. Elasticsearch is now a well-known, widely used piece of software with built-in commercial support and ecosystem—just look at Logstash, Kibana, or any additional plugins. The functionality of this search server is also constantly growing. There are some new features such as the aggregation framework, which opens new use cases—this is where Elasticsearch shines. This development caused the previous book to get outdated quickly. It was also a great challenge to keep up with these changes. The differences between the beta release candidates and the final version caused us to introduce changes several times during the writing.

Now, it is time to say thank you.

Thanks to all the people involved in creating Elasticsearch, Lucene, and all of the libraries and modules published around these projects or used by these projects.

I would also like to thank the team working on this book. First of all, a thank you to the people who worked on the extermination of all my errors, typos, and ambiguities. Many thanks to all the people who send us remarks or write constructive reviews. I was surprised and encouraged by the fact that someone found our work useful.

Last but not least, thanks to all my friends who withstood me and understood my constant lack of time.