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 (
    350592, 351862, 354203, 356480, 356560, 
    352897, 356801, 358945, 349757, 356497, 
    356655, 353178, 356621, 350319, 357585, 
    359008, 359423, 357930, 352714, 356443, 
    356820, 356985, 352282, 352085, 354417, 
    355651, 350568, 357383, 353410, 354653, 
    350662, 350975, 351747, 351892, 352001, 
    352747, 357301, 350152, 350702, 352610, 
    353056, 352021, 354389, 354942, 359333, 
    350645, 352146, 351489, 351559, 354382, 
    353005, 353543, 354867, 356810, 350934, 
    358064, 350921, 351928, 357077, 359076, 
    351691, 354804, 355599, 354563, 357575, 
    350464, 349744, 354771, 349701, 349734, 
    349789, 352000, 352373, 352559, 354400, 
    355170, 357736, 358536, 358989, 359320, 
    350473, 353799, 358182, 352578, 353895, 
    356669, 349735, 353312, 353424, 351936, 
    358007, 350147, 350705, 352078, 354094, 
    354802, 356694, 351931, 353703, 350055
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00477

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "140.18"
    },
    "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": 100,
      "rows_produced_per_join": 100,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "120.18",
        "eval_cost": "20.00",
        "prefix_cost": "140.18",
        "data_read_per_join": "682K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`webmarco`.`cscart_product_descriptions`.`product_id` in (350592,351862,354203,356480,356560,352897,356801,358945,349757,356497,356655,353178,356621,350319,357585,359008,359423,357930,352714,356443,356820,356985,352282,352085,354417,355651,350568,357383,353410,354653,350662,350975,351747,351892,352001,352747,357301,350152,350702,352610,353056,352021,354389,354942,359333,350645,352146,351489,351559,354382,353005,353543,354867,356810,350934,358064,350921,351928,357077,359076,351691,354804,355599,354563,357575,350464,349744,354771,349701,349734,349789,352000,352373,352559,354400,355170,357736,358536,358989,359320,350473,353799,358182,352578,353895,356669,349735,353312,353424,351936,358007,350147,350705,352078,354094,354802,356694,351931,353703,350055)) and (`webmarco`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}