Aahh. The way you phrased your question was pretty ambiguous.

The other posters have good answers. One thing to consider for a smooth interaction would be to eagerly load the next x elements before they scroll into view.

Yeah I’d assume you’d eagerly load enough to make sure everything gets at least partially into the viewport, and maybe a fee more to optimize for network latency. And then perhaps track elements whose trailing ends are not in the viewport, and load more once those become fully visible?