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 (
    2016, 41444, 796, 787, 2469, 3998, 48850, 
    41430, 4729, 2317, 33701, 37885, 23172, 
    18749, 4465, 18747, 4362, 4301, 2452, 
    2459, 2163, 5830, 1482, 3619, 4271, 
    5642, 1756, 1054, 2231, 47604, 36684, 
    41017
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.12311

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 (2016,41444,796,787,2469,3998,48850,41430,4729,2317,33701,37885,23172,18749,4465,18747,4362,4301,2452,2459,2163,5830,1482,3619,4271,5642,1756,1054,2231,47604,36684,41017) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}