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 (
    94816, 94950, 94951, 95566, 95569, 95571, 
    95574, 95575, 95578, 95579, 95580, 
    95581, 95587, 95588, 95589, 95590, 
    95591, 95629, 95630, 95631, 95632, 
    95633, 95634, 95635, 95636, 95637, 
    95641, 95642, 95643, 95644
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00075

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 (94816,94950,94951,95566,95569,95571,95574,95575,95578,95579,95580,95581,95587,95588,95589,95590,95591,95629,95630,95631,95632,95633,95634,95635,95636,95637,95641,95642,95643,95644)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
94816
94950
94951
95566
95569
95571
95574
95575
95578
95579
95580
95581
95587
95588
95589
95590
95591
95629
95630
95631
95632
95633
95634
95635
95636
95637
95641
95642
95643
95644