Speeding Up Bulk Product Creation (With Variations)

Hi,
I am creating variable products. An Example, I have 9 colors, 9 sizes. Which makes 9×9 = 81 total variations for 1 product.

Foreach variation, below is the function that runs.

function create_product_variation( $product_id, $variation_data, $productColorsAndIDs ){
    // Get the Variable product object (parent)
    $product = wc_get_product($product_id);
    $variation_post = array(
        'post_title'  => $product->get_title(),
        'post_name'   => 'product-'.$product_id.'-variation',
        'post_status' => 'publish',
        'post_parent' => $product_id,
        'post_type'   => 'product_variation',
        'guid'        => $product->get_permalink()
    );

    // Creating the product variation
    $variation_id = wp_insert_post( $variation_post );

    // Get an instance of the WC_Product_Variation object
    $variation = new WC_Product_Variation( $variation_id );

    // Iterating through the variations attributes
    foreach ($variation_data['attributes'] as $attribute => $term_name )
    {
        //Only have 2 attributes, size and color.
        $taxonomy = 'pa_'.$attribute;
        update_post_meta( $variation_id, 'attribute_'.$taxonomy, $term_name );
    }

    // Prices
    $variation->set_price( $variation_data['regular_price'] );
    $variation->set_regular_price( $variation_data['regular_price'] );
    $variation->set_image_id($variation_data['variation_thumbnail_id']);

    $variation->save(); // Save the data

}

Before running the above code, I encapsulate the loop as below:

wp_defer_term_counting( false);     //Speeding Up Bulk Update Tricks
wp_defer_comment_counting( false );  //Speeding Up Bulk Update Tricks

//Here comes the loop, which calls the above function create_product_variation().

wp_defer_term_counting( true );     
wp_defer_comment_counting( true ); 

The creation process is slow even I am on a fast hosting (SiteGround GoGeek hosting plan.) Above code creates 1 product in 1-2 minutes, which is pretty slow, and most of the time, I get gateway 504 errors while running it.

What am I missing here ? How can I optimize it to work faster ?