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 (
    41130, 1306, 6660, 1305, 4785, 37881, 
    4795, 41124, 4789, 20830, 6647, 6650, 
    41423, 41134, 4787, 4793, 41102, 41428, 
    2162, 41424, 1840, 4803, 36496, 41138, 
    41427, 4801, 4799, 2625, 4797, 41426, 
    37895, 19195
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00224

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 (41130,1306,6660,1305,4785,37881,4795,41124,4789,20830,6647,6650,41423,41134,4787,4793,41102,41428,2162,41424,1840,4803,36496,41138,41427,4801,4799,2625,4797,41426,37895,19195) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}