Sandbox

SELECT 
  product_id, 
  short_description, 
  full_description 
FROM 
  cscart_product_descriptions 
WHERE 
  product_id IN (11509, 11511, 11521, 11527) 
  AND lang_code = 'en'

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id"],
      "key": "product_id",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 4,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (11509,11511,11521,11527)",
      "attached_condition": "cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id	short_description	full_description
11509		<ul><li>A two piece Pastry Brush Set (20cm and 21cm) </li><li>Natural bristles </li><li>Easy to use </li><li>Wooden handles </li><li>Suitable for baking and pastry basting</li></ul> <p><br /></p>
11511		<ul><li>A wine bottle stopper and pourer</li><li>Can also be used for oil and vinegar</li><li>Free flowing, flexible, adapting to the bottle neck</li></ul> <p><br /></p>
11521		<ul><li>3 mini porcelain dishes with an Acacia wooden tray</li><li>Suitable for dipping sauces</li><li>Dishwasher and oven safe</li><li>Easily clean the wooden tray with a damp clean cloth</li></ul>
11527		<p>Porcelain and acacia wood.Suitable for dipping and snacks,oven proof and dishwasher safe</p>