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 (
    389621, 389620, 389623, 389624, 389622, 
    389626, 389627, 389625, 282478, 282479, 
    391683, 308674, 308677, 392154, 308679, 
    392152, 392156, 308675, 392155, 308680, 
    308678, 392157, 308673, 392158, 308676, 
    392153
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00240

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "36.45"
    },
    "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": 26,
      "rows_produced_per_join": 26,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "31.25",
        "eval_cost": "5.20",
        "prefix_cost": "36.45",
        "data_read_per_join": "177K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`webmarco`.`cscart_product_descriptions`.`product_id` in (389621,389620,389623,389624,389622,389626,389627,389625,282478,282479,391683,308674,308677,392154,308679,392152,392156,308675,392155,308680,308678,392157,308673,392158,308676,392153)) and (`webmarco`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}