Descriptions:
Andrey Breslav, the creator of Kotlin, joins The Pragmatic Engineer to discuss how one of the world’s most widely used programming languages was designed — and what he is building next in response to AI’s growing role in software development. Breslav traces Kotlin’s origins to 2010, when JetBrains concluded that the Java ecosystem had stagnated: Java 6 introduced no language changes at all, Java 7 made only minor ones, and C# had meanwhile advanced considerably. The mission was to build a language that could interoperate seamlessly with existing Java code — a constraint Breslav describes as a far larger undertaking than it appeared, shaping almost every design decision Kotlin made.
The conversation covers specific language design tradeoffs with unusual candor. Pattern matching was deferred because implementing it properly was roughly the size of an entire language; instead, Kotlin’s `when` expression combined with smart casts covers approximately 80% of the practical use cases at a fraction of the complexity. The ternary operator was omitted because Kotlin treats `if` as an expression — a design Breslav now calls one of his biggest regrets, underestimating how much developers relied on it. He also reflects on Google’s announcement of Kotlin as the official Android language, which even surprised the Kotlin team.
The second half of the episode turns to Codespeak, Breslav’s new project: a programming language built on English, designed explicitly for an era where AI writes most of the code. Rather than optimizing for human readability in the traditional sense, Codespeak explores what a language might look like when the primary author and primary reader are both AI models — a genuinely novel design constraint that has significant implications for the future of software tooling.
📺 Source: The Pragmatic Engineer · Published February 12, 2026
🏷️ Format: Interview
