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 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    84695, 88937, 87877, 90124, 90125, 90127, 
    90128, 88515, 88518, 87282, 87290, 
    88514, 88517, 88511, 87876, 88506, 
    88507, 88510, 90828, 90827, 87995, 
    87882, 86861, 87875, 90826, 87881, 
    87787, 87786, 87874, 87792
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.52"
    },
    "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": 30,
      "rows_produced_per_join": 30,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "10.52",
        "eval_cost": "3.00",
        "prefix_cost": "13.52",
        "data_read_per_join": "114K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (84695,88937,87877,90124,90125,90127,90128,88515,88518,87282,87290,88514,88517,88511,87876,88506,88507,88510,90828,90827,87995,87882,86861,87875,90826,87881,87787,87786,87874,87792)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}