It is hard to argue that Kotlin is not an amazing language. What is easy to argue is that there are many unknowns about its performance in the wild and at scale, which makes it hard to make an informed decision about incorporating it into your app. Fortunately for you, we went there and have lived to tell the tale. After more than a year of maintaining a pure Kotlin app at Highlight, and more recently helping Pinterest ramp up Kotlin in Android, we've learned much about the ramifications of moving away from Java. Come learn from our mistakes and successes as we cover the highs, and lows, of using Kotlin in the wild!