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 (
    450261, 416995, 446789, 426059, 409013, 
    414886, 444321, 406390, 408586, 425085, 
    413163, 415231, 429505, 404254, 401286, 
    447216, 440066, 456947, 406411, 404724, 
    416102, 419585, 417300, 439809, 410868, 
    452526, 440855, 429487, 429075, 407708, 
    457100, 449639
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00216

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.0564324,
    "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": 32,
          "cost": 0.0564324,
          "filtered": 100,
          "attached_condition": "cscart_product_descriptions.product_id in (450261,416995,446789,426059,409013,414886,444321,406390,408586,425085,413163,415231,429505,404254,401286,447216,440066,456947,406411,404724,416102,419585,417300,439809,410868,452526,440855,429487,429075,407708,457100,449639) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}