create index for following LARAVEL eloquent query - php

Question

Hi I have more than 500k records in items table Its takes more than 9 seconds to execute this query ineed to make it milliseconds to execute this query using mysql index
$products = \App\items::with([
'item_store' => function($query) {
$query->select('size', 'item_id', 'item_store_id');
},
'pics' => function($query) {
$query->select('img_url', 'item_id');
},
'brand' => function($query) {
$query->select('item_id', 'brand_id');
},
'brand.brand' => function($query) {
$query->select('brand_id', 'brand_name');
}
])
->select('item_id', 'short_name', 'price', 'price_above')
->orderBy('Price', 'Asc')->whereIn('category_id', $arr)
->groupBy('Sku')
->paginate(20);
my database structure is [st] https://screenshots.firefox.com/JAmaKENMYRhQkEjx/ourweds.com
this is item table migration
Schema::create('item', function (Blueprint $table) {
$table->bigIncrements('item_id');
$table->string('item_name');
$table->integer('Sku');
$table->text('Description');
$table->text('short_description');
$table->text('category_id');
$table->string('color');
$table->double('price');
$table->double('indian_price');
$table->string('old_price');
$table->string('indian_old_price');
$table->timestamps();
});
item eloquent model
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class items extends Model
{
//
protected $table = 'items';
protected $primaryKey = 'item_id';
protected $fillable = [
'category_id',
'item_name',
'Sku',
'Description',
'short_description',
'color',
'kik_cash_percentage',
'status',
'price',
'price_old',
'indian_price',
'short_name',
'price_above',
'short_name_alter',
'availability'
];
public function pics(){
return $this->hasOne( 'App\item_pics', 'item_id' );
}
public function item_store()
{
return $this->hasMany('App\item_store','item_id');
}
public function category()
{
return $this->belongsTo('App\categories','category_id');
}
public function brand()
{
return $this->hasOne('App\item_has_brand','item_id');
}
}