This is my second book on Elasticsearch, and I am really fascinated by the love and feedback I got from the readers of my first book, Elasticsearch Essentials. The book you are holding covers Elasticsearch 5.x, the release of Elasticsearch that brings a whole lot of features and improvements to this great search server. Hopefully, after reading this book, you will not only get to know the underlying architecture of Lucene and Elasticsearch, but also posses a command over many advanced concepts, such as scripting, improving cluster performance, writing custom Java-based plugins, and many more.

Now it is time to say thank you.

I would like to thank my family for their continuous support, especially my brother, Patanjali Dixit, who has been a pillar of strength for me at each step throughout my career. I extend my big thanks to Lavleen for the love, support, and encouragement she gave during all those days when I was busy writing this book or solving complex problems at work.

I would like to extend my thanks to the Packt team working on this book, including our technical reviewer. Without their incredible support, the book wouldn't have been as great as it is now.

I would also like to thank all the people I'm working with at Sentieo for all their love and for creating a culture that helps make work more fun. At Sentieo, I extend my special thanks to Atul Shah, who always inspired me to go into the intricacies of Lucene and Elasticsearch and solve some really complex problems using these technologies.

Finally, thanks to Shay Banon for creating Elasticsearch and to all the people who contributed to the libraries and modules published around this project.

Once again, thank you.