The four states

Every network request has four states, and if you only show one of them, you're building a demo, not a real product.

The first is loading: if you don't show it, the user thinks the button is broken and clicks it ten times. The second is success. The third is failure, where you show a message that tells the user what to do next. The fourth is success with an empty result, the one people forget most often, because an empty list with no message at all looks like a bug.

Disable the button while loading. It's the simplest way to stop two requests from going out at the same time.