SELECT 
  parent_option_id, 
  child_option_id, 
  parent_variant_id, 
  child_variant_id 
FROM 
  cscart_nested_option_rules 
WHERE 
  product_id = 12684 
ORDER BY 
  parent_option_id, 
  child_option_id, 
  position, 
  nested_rule_id

Query time 0.00454

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.40"
    },
    "ordering_operation": {
      "using_filesort": true,
      "table": {
        "table_name": "cscart_nested_option_rules",
        "access_type": "ref",
        "possible_keys": [
          "idx_product",
          "idx_product_parent"
        ],
        "key": "idx_product",
        "used_key_parts": [
          "product_id"
        ],
        "key_length": "4",
        "ref": [
          "const"
        ],
        "rows_examined_per_scan": 4,
        "rows_produced_per_join": 4,
        "filtered": "100.00",
        "cost_info": {
          "read_cost": "1.00",
          "eval_cost": "0.40",
          "prefix_cost": "1.40",
          "data_read_per_join": "128"
        },
        "used_columns": [
          "nested_rule_id",
          "product_id",
          "parent_option_id",
          "child_option_id",
          "parent_variant_id",
          "child_variant_id",
          "position"
        ]
      }
    }
  }
}