'hayksaakian mentioned toasts, which are global, but I think another option would be "toasts" local to the button. E.g. flash a checkmark next to the button user clicked for a second, indicating the action was registered and completed. Key here is: next to, and asynchronous. The checkmark can stay alive for a second, but the button shouldn't be blocked for that time. If the user clicks it again immediately, it should "refresh" the success indicator, or add another one.

UIs in games have this solved in countless of ways.