SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    3983, 3984, 3981, 3985, 3982, 4681, 4683, 
    4679, 4685, 4677, 4682, 4678, 4680, 
    4684, 4451
  )

Query time 0.00039

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": 15,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (3983,3984,3981,3985,3982,4681,4683,4679,4685,4677,4682,4678,4680,4684,4451)"
    }
  }
}