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 (
    90907, 90908, 90986, 90987, 85082, 85168, 
    85214, 85260, 83038, 90874, 90953, 
    82622, 85119, 85122, 86189, 86212, 
    86521, 86797, 90564, 90570, 90576, 
    89073, 83069, 83622, 90905, 90984, 
    85080, 85166, 85212, 85258
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00084

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 (90907,90908,90986,90987,85082,85168,85214,85260,83038,90874,90953,82622,85119,85122,86189,86212,86521,86797,90564,90570,90576,89073,83069,83622,90905,90984,85080,85166,85212,85258)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}