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 (
    97887, 97889, 98421, 98424, 98425, 98426, 
    98428, 98432, 98434, 98436, 98437, 
    98438, 98442, 98446, 98449, 98450, 
    98452, 98455, 98485, 98486, 98487, 
    98488, 98489, 98491, 98493, 98494, 
    98495, 98503, 98504, 98505, 98506, 
    98507, 98508, 98722, 98723, 98724, 
    98725, 98726, 98727, 98728, 98729, 
    98730, 98731, 98732, 98733, 98734, 
    98735, 98736
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00094

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.63"
    },
    "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": 48,
      "rows_produced_per_join": 48,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "16.83",
        "eval_cost": "4.80",
        "prefix_cost": "21.63",
        "data_read_per_join": "183K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (97887,97889,98421,98424,98425,98426,98428,98432,98434,98436,98437,98438,98442,98446,98449,98450,98452,98455,98485,98486,98487,98488,98489,98491,98493,98494,98495,98503,98504,98505,98506,98507,98508,98722,98723,98724,98725,98726,98727,98728,98729,98730,98731,98732,98733,98734,98735,98736)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
97887
97889
98421
98424
98425
98426
98428
98432
98434
98436
98437
98438
98442
98446
98449
98450
98452
98455
98485
98486
98487
98488
98489
98491
98493
98494
98495
98503
98504
98505
98506
98507
98508
98722
98723
98724
98725
98726
98727
98728
98729
98730
98731
98732
98733
98734
98735
98736