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, 50194, 41341, 41340, 47922, 47921, 
    41343, 47896, 47924, 47923, 31632, 
    31634, 31631, 41339, 2303, 31627, 31965, 
    26880, 26895, 26894, 26876, 26885, 
    26881, 26884, 26883, 31629, 41397, 
    1972, 31630, 3764, 36746, 2085
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00977

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 (50216,50194,41341,41340,47922,47921,41343,47896,47924,47923,31632,31634,31631,41339,2303,31627,31965,26880,26895,26894,26876,26885,26881,26884,26883,31629,41397,1972,31630,3764,36746,2085) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}