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 (
    98749, 98758, 99561, 99570, 99571, 99572, 
    99573, 99580, 99581, 99582, 99583, 
    99584, 99585, 99586, 99587, 100067, 
    100068, 100069, 100070, 100071, 100072, 
    100150, 100151, 100152, 100153, 100154, 
    100155, 100156, 100169, 100170
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00036

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 (98749,98758,99561,99570,99571,99572,99573,99580,99581,99582,99583,99584,99585,99586,99587,100067,100068,100069,100070,100071,100072,100150,100151,100152,100153,100154,100155,100156,100169,100170)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}