Ajax read large json file slowly - json

Question

I am using AJAX to read a large JSON file (about 15 MB minified), in order to display autocomplete suggestions on a text field.
The problem is that after user types 4 characters in order the suggestions to begin, i have to wait around 20 to 60 seconds which makes actually impossible to use it.
I don't know any techniques how i could make it read the JSON file faster.
I would like to read your suggestions...
My AJAX request is :
$(document).ready(function () {
$("#card").autocomplete({
source: function (request, response) {
$.ajax({
dataType: "json",
data: {
term: request.term,
},
type: 'GET',
contentType: 'application/json; charset=utf-8',
xhrFields: {
withCredentials: true
},
cache: true,
url: base_url+'/test123/wp-content/plugins/trading-collectible-cards/public/js/AllSets.json',
success: function (data) {
var keys = Object.getOwnPropertyNames (data)
var outputArray;
$.each(keys,function(ele, val){
var array = $.map(data[val].cards, function (set) {
return {
label: set.name + " (" +data[val].name + ")",
value: set.name,
text: set.text,
multi: set.multiverseid,
rarity: set.rarity,
setname:keys[ele],
setfull:data[val].name
}
});
if (ele == 0)
outputArray = $.merge([], array);
else {
outputArray = $.merge(outputArray, array);
}
});
response($.ui.autocomplete.filter(outputArray, request.term));
},
error: function (data) {
}
});
},
minLength: 3,
open: function () {
},
close: function () {
},
focus: function (event, ui) {
},
select: function (event, ui) {
$( "#card" ).val( ui.item.label );
$( "#description" ).html( ui.item.text );
}
});