I am grateful to Packt Publishing for offering me the possibility to write this book. You are great and so is your team. Thank you Divij, Chaitanya, Prajakta, and the whole Packt team for being awesome and supporting me through all this journey in such a friendly and warm way.

Quality is something that is difficult to achieve when working on something on your own. Thank you, Packt team, you've been awesome. And a big special gratitude goes to Romania, to Bogdan, who thoroughly reviewed the book, ran all the code snippets, tests, and lint. Bogdan's attention to even the most tiny details is astonishing. The book was rewritten after Bogdan's comments, and it became so much cleaner. Thank you very much, Bogdan and Alex, for the recommendation.

Time. Support. Love. When you have these three things you are happy and any challenge in the world can scare you. When you have these three things you know that you are capable of everything. When you have these three things you have power. But you can never have these things alone. That is why you must be eternally grateful to those who provide time, support, and love to you.

That is why my big thanks goes to my company where I am currently working—Meetrics. Meetrics provided me with time to write the book. They trusted me and allowed me to use a fraction of my working time for writing the book. Thank you very much!

I want to thank to all my friends and colleagues who supported me during this journey. Every time I come to Meetrics my team asks me how the book is going. Every time we're going to Portugal or Ukraine, our friends and family ask. Every day my friends from Berlin ask me how is it going. Thank you, people, you are awesome! Thank you, EdEra team, for being amazing and postponing important tasks because of my book.

I would love to express gratitude to my parents for educating me with so much love that I know that I am capable of anything. I know that I will not fail. Thank you for all your love and support. Thank you for giving me this confidence in myself. I want to thank to my lovely daughter, whose love and help keeps me going and continuing what I'm doing, knowing that all this is not for nothing. I want to thank to my brother for all the fun we share even and mostly while we're working.

And I want to address a special thanks with love to my husband. Along this writing journey Rui has given me time, support, and love. Rui did everything at home so I could have all the time for writing. Rui felt every slight change in my mood and provided support during all of them so I could feel comfortable again and write. If I would stay up the whole night writing and needed someone to be nearby, Rui would stay up the whole night. For every chapter in the book, Rui was the first person to review them. This was invaluable feedback. Rui gave me chapters back full of corrections and I felt sad. But then he would say something like: Oh my god, Olga, this chapter is amazing! I understood everything! I am looking forward for the next chapter to see what's next! When someone who you love very much tells you this, you just want to move on and continue your amazing writing. Thank you very much for this!