Frustratingly, we can't actually look at the React code he used, because it is Google proprietary code(?). But there are definitely slow and fast ways to take an array of elements and render it. Ideally, each element would be wrapped in a component with a "key" property to speed up diffing.

Also, the standard way to do infinite scrolling when you care about performance, especially on mobile, is to reuse a small number of elements, just enough to cover the screen and then some. You don't actually create 1500 elements.