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 (
    100376, 100377, 100378, 100379, 100380, 
    100381, 100382, 100383, 100598, 100599, 
    100600, 100601, 100602, 100603, 100604, 
    100605, 100606, 100607, 100608, 100609, 
    100610, 100611, 100654, 100655, 100656, 
    100657, 100658, 100659, 100660, 100661, 
    100662, 100663, 100664, 100696, 100697, 
    100698, 100699, 100884, 100885, 100886, 
    100887, 100900, 100901, 100902, 100903, 
    100904, 100907, 100908
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00105

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 (100376,100377,100378,100379,100380,100381,100382,100383,100598,100599,100600,100601,100602,100603,100604,100605,100606,100607,100608,100609,100610,100611,100654,100655,100656,100657,100658,100659,100660,100661,100662,100663,100664,100696,100697,100698,100699,100884,100885,100886,100887,100900,100901,100902,100903,100904,100907,100908)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}