India alone has an estimated 600–650 million active Android smartphones. Behind many of these devices are Android SDKs built and shipped by OEMs and partner teams, powering experiences that need to work across different Android versions, build systems, app architectures, and release pipelines. Building an Android SDK for production is fundamentally different from building an Android application. Your consumers aren't end users—they're engineering teams integrating your SDK into applications that you don't own or control. Once an APK becomes an SDK, entirely new engineering challenges emerge. Before writing a single line of SDK code, there are important architectural decisions to make. Should the SDK be modular or monolithic? How should public APIs evolve without breaking consumers? How do you design for backward compatibility, extensibility, and OEM-specific requirements while keeping integrations simple and reliable? In this talk, we'll explore the system design principles behind production-grade Android SDKs and the engineering challenges that arise once they are shipped at scale. We'll discuss SDK architecture and modularization strategies, public API design, dependency graph analysis, native libraries, resource packaging, release pipelines, versioning strategies, and SDK size optimizations. We'll also cover practical lessons learned while shipping Android SDKs to OEMs and partner applications—ranging from transitive dependency conflicts and build system incompatibilities to release management, SDK size constraints, and consumer app integration challenges that only surface once your SDK lands inside someone else's codebase. By the end of the session, you'll have a practical framework for architecting Android SDKs that are scalable, extensible, and easier to integrate across diverse Android environments. If you've ever wondered why your perfectly working APK suddenly breaks after becoming an SDK—or how to architect an Android SDK that survives years of integrations and releases—this talk is for you.