Make a php array load faster - php

Question

I successfully edited the checkout page of the WooCommerce city field in order to be a dropdown field with a lot of cities in it around 13k values the problem is that on mobile and some low-end devices this field isn't performing well how I can make this array load faster is a DB call worth it in this situation, is there any way stop the dropdown and make the field only searchable is it worth splitting the array or loading from a text file?
The code I made
<?php
// Add custom checkout select fields
add_filter('woocommerce_checkout_fields', 'add_custom_checkout_select_fields');
function add_custom_checkout_select_fields($fields)
{
$arr = array(); // very big array arround 13k values
// Define HERE in the array, your desired cities
$cities = $arr;
// Format in the right way the options array of cities
$options = array(
'' => __('Choose City', 'woocommerce') . '…'
);
foreach ($cities as $city)
{
$options[$city] = $city;
}
// Adding 2 custom select fields
$fields['billing']['billing_city2'] = $fields['shipping']['shipping_city2'] = array(
'type' => 'select',
'required' => true,
'options' => $options,
'autocomplete' => 'address-level2',
'input_class' => array(
'wc-enhanced-select',
)
);
// Copying data from WooCommerce city fields
$fields['billing']['billing_city2']['class'] = array_merge($fields['billing']['billing_city']['class'], array(
'hidden'
));
$fields['shipping']['shipping_city2']['class'] = array_merge($fields['shipping']['shipping_city']['class'], array(
'hidden'
));
$fields['billing']['billing_city2']['label'] = $fields['billing']['billing_city']['label'];
$fields['shipping']['shipping_city2']['label'] = $fields['shipping']['shipping_city']['label'];
$fields['billing']['billing_city2']['priority'] = $fields['billing']['billing_city']['priority'] + 5;
$fields['shipping']['shipping_city2']['priority'] = $fields['shipping']['shipping_city']['priority'] + 5;
wc_enqueue_js("
jQuery( ':input.wc-enhanced-select' ).filter( ':not(.enhanced)' ).each( function() {
var select2_args = { minimumResultsForSearch: 1 };
jQuery( this ).select2( select2_args ).addClass( 'enhanced' );
});");
return $fields;
}