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 (
    99571, 99572, 99580, 99582, 99584, 99586, 
    100067, 100069, 100072, 100152, 100153, 
    100156, 100169, 100171, 100173, 100176, 
    100178, 100180, 100321, 100323, 100326, 
    100605, 100606, 100610, 100884, 100887, 
    100900, 100903, 100907, 100910
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00077

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 (99571,99572,99580,99582,99584,99586,100067,100069,100072,100152,100153,100156,100169,100171,100173,100176,100178,100180,100321,100323,100326,100605,100606,100610,100884,100887,100900,100903,100907,100910)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}