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 (
    36305, 5645, 41363, 45282, 925, 41388, 
    32367, 4857, 25896, 4868, 935, 35181, 
    5764, 41138, 35183, 1275, 5771, 26866, 
    47610, 43459, 3598, 40753, 5268, 41427, 
    41359, 37848, 2640, 5259, 33704, 5760, 
    4817, 41011
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00389

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 (36305,5645,41363,45282,925,41388,32367,4857,25896,4868,935,35181,5764,41138,35183,1275,5771,26866,47610,43459,3598,40753,5268,41427,41359,37848,2640,5259,33704,5760,4817,41011) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}