SELECT 
  a.category_id 
FROM 
  cscart_categories as a 
  LEFT JOIN cscart_categories as b ON b.category_id IN (7435) 
WHERE 
  a.id_path LIKE CONCAT(b.id_path, '/%')

Query time 0.00180

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1494.60"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "b",
          "access_type": "const",
          "possible_keys": [
            "PRIMARY",
            "p_category_id"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "category_id"
          ],
          "key_length": "3",
          "ref": [
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.00",
            "eval_cost": "0.20",
            "prefix_cost": "0.00",
            "data_read_per_join": "5K"
          },
          "used_columns": [
            "category_id",
            "id_path"
          ]
        }
      },
      {
        "table": {
          "table_name": "a",
          "access_type": "index",
          "key": "id_path",
          "used_key_parts": [
            "id_path"
          ],
          "key_length": "767",
          "rows_examined_per_scan": 6988,
          "rows_produced_per_join": 776,
          "filtered": "11.11",
          "using_index": true,
          "cost_info": {
            "read_cost": "97.00",
            "eval_cost": "155.27",
            "prefix_cost": "1494.60",
            "data_read_per_join": "4M"
          },
          "used_columns": [
            "category_id",
            "id_path"
          ],
          "attached_condition": "(`webmarco`.`a`.`id_path` like <cache>(concat('6473/7080/7435','/%')))"
        }
      }
    ]
  }
}

Result

category_id
8066
8112
8113
8114
8115
8116
8117
8118
8119
8120
8121
8122
8123
8124
8125
8126
8127
8151
8152
8153
8229
8230
8231
8232
8233
8234
8235
8236
8237
8238
8239
8240
8241
8242
8243
8244
8245
8246
8247
8248
8249