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, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    442715, 430741, 406089, 410471, 409489, 
    412459, 424229, 448141, 452096, 435935, 
    450361, 410461, 454777, 444113, 417555, 
    428819, 454049, 459252, 405167, 401806, 
    425534, 458860, 447690, 422606
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00091

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.04252208,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["product_id", "lang_code"],
          "loops": 1,
          "rows": 24,
          "cost": 0.04252208,
          "filtered": 100,
          "attached_condition": "cscart_product_descriptions.product_id in (442715,430741,406089,410471,409489,412459,424229,448141,452096,435935,450361,410461,454777,444113,417555,428819,454049,459252,405167,401806,425534,458860,447690,422606) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}