Another solution is to disable the button so that the user can't click it twice in a row. Adapt the following logic to your code.
//Bind a click event handler to your button
$("body").on("click", "you_button_selector", function(e)
{
//Prevent any default behaviour, we're dealing with this ourselves
e.preventDefault();
//First, disable the button
$("your_button_selector").attr("disabled", "disabled");
//Then, make your ajax call
$.ajax(
{
url: "http://example.com",
success: function(data)
{
//When your ajax call returns, enable the button again
$("your_button_selector").removeAttr("disabled");
}
});
});