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 (
    91774, 91776, 91778, 91780, 92526, 91783, 
    91784, 91777, 91779, 92525, 92532, 
    92524, 92527, 92528, 92539, 92531, 
    92538, 92529, 92530, 92523, 92536, 
    92540, 90702, 90706, 90648, 90687, 
    90629, 92537, 90714, 90720
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00095

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 (91774,91776,91778,91780,92526,91783,91784,91777,91779,92525,92532,92524,92527,92528,92539,92531,92538,92529,92530,92523,92536,92540,90702,90706,90648,90687,90629,92537,90714,90720)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}