Ente’s photo gallery is a production Flutter interface that must remain smooth as users’ libraries grow. Its original implementation did not: scrolling became increasingly janky at scale. This talk examines why it failed and how we arrived at the solution that shipped. We built several prototypes, starting with Flutter’s simplest and most maintainable built-in approaches. None met Ente’s performance requirements at scale, so we moved towards more complex solutions. We’ll walk through each prototype in turn, using its benchmarking and profiling results to show where performance broke down and explain the underlying Flutter behaviour. Finally, we’ll unpack the solution: a custom render sliver backed by precomputed gallery geometry. In explaining why it worked, we’ll explore Flutter’s sliver layout protocol. Key takeaways: 1. Reliably benchmark different implementations and identify performance issues using timeline traces in Flutter DevTools’ Performance view. 2. Understand why the built-in lazy-scrolling approaches we tested did not meet Ente’s requirements at scale. 3. Develop an understanding of Flutter’s sliver layout protocol. 4. See how a performance problem in a production app was diagnosed and solved end-to-end.