[KotlinConf2025] Blueprints for Scale: What AWS Learned Building a Massive Multiplatform Project
Ian Botsford and Matis Lazdins from Amazon Web Services (AWS) shared their experiences and insights from developing the AWS SDK for Kotlin, a truly massive multiplatform project. This session provided a practical blueprint for managing the complexities of a large-scale Kotlin Multiplatform (KMP) project, offering firsthand lessons on design, development, and scaling. The speakers detailed the strategies they adopted to maintain sanity while dealing with a codebase that spans over 300 services and targets eight distinct platforms.
Architectural and Development Strategies
Botsford and Lazdins began by breaking down the project’s immense scale, explaining that it is distributed across four different repositories and consists of nearly 500 Gradle projects. They emphasized the importance of a well-defined project structure and the strategic use of Gradle to manage dependencies and build processes. A key lesson they shared was the necessity of designing for Kotlin Multiplatform from the very beginning, rather than attempting to retrofit it later. They also highlighted the critical role of maintaining backward compatibility, a practice that is essential for a project with such a large user base. The speakers explained the various design trade-offs they had to make and how these decisions ultimately shaped the project’s architecture and long-term sustainability.
The Maintainer Experience
The discussion moved beyond technical architecture to focus on the human element of maintaining such a vast project. Lazdins spoke about the importance of automating repetitive and mundane processes to free up maintainers’ time for more complex tasks. He detailed the implementation of broad checks to catch issues before they are merged, a proactive approach that prevents regressions and ensures code quality. These checks are designed to be highly informative while remaining overridable, giving developers the autonomy to make informed decisions. The presenters stressed that a positive maintainer experience is crucial for the health of any large open-source project, as it encourages contributions and fosters a collaborative environment.
Lessons for the Community
In their concluding remarks, Botsford and Lazdins offered a summary of the most valuable lessons they learned. They reiterated the importance of owning your own dependencies, structuring projects for scale, and designing for KMP from the outset. By sharing their experiences with a real-world, large-scale project, they provided the Kotlin community with actionable insights that can be applied to projects of any size. The session served as a powerful testament to the capabilities of Kotlin Multiplatform and the importance of a thoughtful, strategic approach to software development at scale.