For consistent runtime performance -- UI should meet the needs of being responsive to user interactions (clicks, taps, scrolls, etc), rendering smooth animations, and fetching and rendering content in time. It is too difficult for web devs to reason about rendering pipeline and how to use combination of microtasks, rAF, settimeout, postmessage etc to achieve this. This talk covers our journey in developing a native scheduling API that can schedule browser tasks, framework code, application code, and third party code.