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 (
    403166, 443366, 406831, 433693, 445954, 
    441514, 409350, 459209, 410927, 406634, 
    450452, 453579, 428056, 419040, 408601, 
    433947, 418245, 450170, 460049, 430800, 
    435777, 452645, 446157, 434819, 439332, 
    410664, 457167, 442668, 438623, 443841, 
    442218, 414148, 426118, 460489, 445497, 
    420289, 445023, 406489, 425857, 423797, 
    409307, 457277, 414945, 450623, 417564, 
    405376, 423809, 415249
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00260

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 (403166,443366,406831,433693,445954,441514,409350,459209,410927,406634,450452,453579,428056,419040,408601,433947,418245,450170,460049,430800,435777,452645,446157,434819,439332,410664,457167,442668,438623,443841,442218,414148,426118,460489,445497,420289,445023,406489,425857,423797,409307,457277,414945,450623,417564,405376,423809,415249) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}