SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    9858, 9859, 9860, 9861, 9862, 9863, 9814, 
    9815, 9816, 9817, 9818, 9820, 9821, 
    9822, 9823, 9824
  )

Query time 0.00053

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": 16,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (9858,9859,9860,9861,9862,9863,9814,9815,9816,9817,9818,9820,9821,9822,9823,9824)"
    }
  }
}