SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    15959, 15960, 15961, 15962, 10100, 10175, 
    10101, 10644, 10606, 10177, 10178, 
    10643, 10102, 9940, 15965, 15966, 9905, 
    9904, 10041, 10053
  )

Query time 0.00058

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 20,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (15959,15960,15961,15962,10100,10175,10101,10644,10606,10177,10178,10643,10102,9940,15965,15966,9905,9904,10041,10053)"
    }
  }
}