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 (
    427389, 404082, 444676, 437249, 431522, 
    404419, 429796, 418742, 413554, 456683, 
    423476, 406110, 401379, 401218, 455612, 
    434688, 408741, 404021, 450232, 458363, 
    414802, 433182, 441236, 438649, 456473, 
    419639, 438982, 402302, 442349, 442173, 
    415468, 455700, 413775, 422178, 405950, 
    436262, 417156, 412957, 447950, 452843, 
    421121, 421884, 451854, 423912, 449116, 
    421546, 415507, 439646
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00212

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.08425304,
    "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": 48,
          "cost": 0.08425304,
          "filtered": 100,
          "attached_condition": "cscart_product_descriptions.product_id in (427389,404082,444676,437249,431522,404419,429796,418742,413554,456683,423476,406110,401379,401218,455612,434688,408741,404021,450232,458363,414802,433182,441236,438649,456473,419639,438982,402302,442349,442173,415468,455700,413775,422178,405950,436262,417156,412957,447950,452843,421121,421884,451854,423912,449116,421546,415507,439646) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}