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 (
    86740, 89740, 89741, 83228, 83229, 83230, 
    83231, 85328, 85329, 85425, 85426, 
    85476, 85477, 85527, 85528, 86605, 
    86606, 86674, 86675, 83458, 84299, 
    84300, 85042, 85043, 85090, 85176, 
    85222, 85268, 85345, 82842
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00109

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 (86740,89740,89741,83228,83229,83230,83231,85328,85329,85425,85426,85476,85477,85527,85528,86605,86606,86674,86675,83458,84299,84300,85042,85043,85090,85176,85222,85268,85345,82842)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}