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 (
    50216, 47597, 18608, 27359, 3713, 37096, 
    27354, 27357, 27358, 27360, 27362, 
    36399, 19386, 27363, 3662, 36339, 3666, 
    637, 2553, 534, 25180, 3004, 47603, 
    37097, 47610, 43459, 43460, 41369, 
    43461, 40928, 43842, 43841
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.01771

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 (50216,47597,18608,27359,3713,37096,27354,27357,27358,27360,27362,36399,19386,27363,3662,36339,3666,637,2553,534,25180,3004,47603,37097,47610,43459,43460,41369,43461,40928,43842,43841) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}