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 (
    38159, 32312, 33282, 647, 27921, 23992, 
    3010, 6521, 2236, 5143, 3514, 46696, 
    25245, 2872, 649, 376, 29732, 2584, 
    3190, 32318, 33132, 3195, 48822, 32305, 
    6109, 5647, 813, 2858, 36573, 6646, 
    1973, 35483
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00361

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "11",
          "used_key_parts": ["product_id", "lang_code"],
          "rows": 32,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (38159,32312,33282,647,27921,23992,3010,6521,2236,5143,3514,46696,25245,2872,649,376,29732,2584,3190,32318,33132,3195,48822,32305,6109,5647,813,2858,36573,6646,1973,35483) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}