SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '' 
    OR cscart_product_descriptions.short_description IS NULL, 
    cscart_product_descriptions.full_description, 
    ''
  ) AS full_description, 
  cscart_product_descriptions.meta_keywords, 
  cscart_product_descriptions.meta_description, 
  cscart_product_descriptions.search_words, 
  cscart_product_descriptions.promo_text 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    4579, 4580, 4581, 4582, 4583, 4584, 4585, 
    4586, 4588, 4589, 4590, 4591, 4592, 
    4593, 4594, 4595, 4597, 4598, 4599, 
    4600, 4601, 4602, 4603, 4604, 4605, 
    4606, 4609
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00055

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "18.91"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 27,
      "rows_produced_per_join": 27,
      "filtered": "100.00",
      "index_condition": "((`primapearl_r_new`.`cscart_product_descriptions`.`product_id` in (4579,4580,4581,4582,4583,4584,4585,4586,4588,4589,4590,4591,4592,4593,4594,4595,4597,4598,4599,4600,4601,4602,4603,4604,4605,4606,4609)) and (`primapearl_r_new`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "16.21",
        "eval_cost": "2.70",
        "prefix_cost": "18.91",
        "data_read_per_join": "102K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "meta_keywords",
        "meta_description",
        "search_words",
        "promo_text"
      ]
    }
  }
}