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 (
    90344, 85586, 87962, 88079, 88084, 90327, 
    87994, 90317, 90319, 90320, 85645, 
    87388, 88390, 91428, 91430, 88395, 
    86887, 85581, 88389, 88391, 88388, 
    88095, 88392, 92408, 87993, 91427, 
    91429, 87387, 87389, 87383
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00092

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 (90344,85586,87962,88079,88084,90327,87994,90317,90319,90320,85645,87388,88390,91428,91430,88395,86887,85581,88389,88391,88388,88095,88392,92408,87993,91427,91429,87387,87389,87383)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}