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 (
    319, 48769, 37304, 38143, 27357, 38152, 
    35249, 2932, 27358, 14822, 41441, 23406, 
    33177, 4004, 36733, 49306, 1897, 3764, 
    3774, 27360, 6577, 33214, 41442, 2926, 
    5411, 47017, 466, 38558, 3168, 40452, 
    44939, 3230
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.03528

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 (319,48769,37304,38143,27357,38152,35249,2932,27358,14822,41441,23406,33177,4004,36733,49306,1897,3764,3774,27360,6577,33214,41442,2926,5411,47017,466,38558,3168,40452,44939,3230) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}