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 (
    630, 3866, 3867, 3568, 3868, 3567, 3869, 
    3870, 3872, 3517, 3516, 3518, 3871, 
    3570, 3569, 3876, 37850, 3577, 1400, 
    3862, 3519, 1401, 3863, 1409, 3578, 
    3864, 3861, 35731, 23261, 1399, 632, 
    3021
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00340

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 (630,3866,3867,3568,3868,3567,3869,3870,3872,3517,3516,3518,3871,3570,3569,3876,37850,3577,1400,3862,3519,1401,3863,1409,3578,3864,3861,35731,23261,1399,632,3021) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}