Andrey Koleshko had his first touch with programming while at school, when he worked on Pascal. He had been solving basic algorithmic tasks. The first programming language he used at the beginning of his career was Java. He worked with this language for a year and then migrated to the Ruby language, which he worked with for the next four years. Of these four years, he worked with Altoros for three. He had an amazing time there, learning the language and technologies deeply. Currently, he works at a local cloud hosting company. The company change provided him with the opportunity to deal with a lot of challenges concerning application architecture, code testing, debugging, and deployment processes. As a result, he has been able to contribute to some famous Ruby libraries. More detailed information about his contributions can be found on GitHub at https://github.com/ka8725. He mostly works with the Rails framework. He openly shares all of his thoughts and his most interesting experiences through his blog at https://railsguides.net. He has recently started to learn the Python programming language. He lives in Minsk, Belarus, and likes to watch and play sports such as soccer, ping-pong, and volleyball. He also likes travelling to tropical countries with his wife. Teaching people gives him immense pleasure.