A few years ago you had to work hard to succeed in some fields. Nowadays you don’t need to work hard but to work smart. So this means that most of the time laziness (of course not extremely) is useful for our productivity. On the other hand, laziness is extremely important when you work with large amount of data and reduced space or power. In this talk we will try to cover all aspects of laziness in Kotlin: starting from lazy initialization of properties using delegates, lazy collections, sequences and, finally, laziness with coroutines. The main thing we would like to talk about is how to use this laziness and be productive with it. To see one more benefit of laziness in Kotlin we’ll refactor a real application to use lazy calculations.