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 (
    98081, 98082, 98083, 98523, 98524, 98525, 
    98526, 98527, 98528, 98529, 98530, 
    98531, 98532, 98533, 98534, 98535, 
    98536, 98537, 98557, 98558, 98559, 
    98773, 98774, 98775, 98776, 98777, 
    98778, 98779, 98780, 98781
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00100

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 (98081,98082,98083,98523,98524,98525,98526,98527,98528,98529,98530,98531,98532,98533,98534,98535,98536,98537,98557,98558,98559,98773,98774,98775,98776,98777,98778,98779,98780,98781)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
98081
98082
98083
98523
98524
98525
98526
98527
98528
98529
98530
98531
98532
98533
98534
98535
98536
98537
98557
98558
98559
98773
98774
98775
98776
98777
98778
98779
98780
98781