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 (
    96636, 96637, 96638, 96639, 96640, 96641, 
    96642, 96643, 96644, 96645, 96646, 
    96647, 96648, 96649, 96650, 96651, 
    96652, 96653, 96654, 96655, 96656, 
    96657, 96658, 96659, 96660, 96661, 
    96662, 96663, 96664, 96665, 96666, 
    96667, 96668, 96669, 96670, 96671, 
    96672, 96673, 96674, 96675, 96676, 
    96678, 96680, 96681, 96682, 96683, 
    96686, 96687
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00089

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "25.69"
    },
    "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": "20.89",
        "eval_cost": "4.80",
        "prefix_cost": "25.69",
        "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 (96636,96637,96638,96639,96640,96641,96642,96643,96644,96645,96646,96647,96648,96649,96650,96651,96652,96653,96654,96655,96656,96657,96658,96659,96660,96661,96662,96663,96664,96665,96666,96667,96668,96669,96670,96671,96672,96673,96674,96675,96676,96678,96680,96681,96682,96683,96686,96687)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
96636
96637
96638
96639
96640
96641
96642
96643
96644
96645
96646
96647
96648
96649
96650
96651
96652
96653
96654
96655
96656
96657
96658
96659
96660
96661
96662
96663
96664
96665
96666
96667
96668
96669
96670
96671
96672
96673
96674
96675
96676
96678
96680
96681
96682
96683
96686
96687