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 (
    85321, 85417, 85418, 85468, 85469, 85519, 
    85520, 86184, 86185, 86207, 86208, 
    86508, 86509, 86784, 86785, 83053, 
    83055, 83602, 83604, 84525, 84526, 
    84591, 84592, 90889, 90891, 90968, 
    90970, 82631, 82855, 82856
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00069

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.21"
    },
    "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": "13.22",
        "eval_cost": "3.00",
        "prefix_cost": "16.22",
        "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 (85321,85417,85418,85468,85469,85519,85520,86184,86185,86207,86208,86508,86509,86784,86785,83053,83055,83602,83604,84525,84526,84591,84592,90889,90891,90968,90970,82631,82855,82856)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}