SELECT 
  GROUP_CONCAT(tag SEPARATOR ', ') 
FROM 
  cscart_tags 
  INNER JOIN cscart_tag_links ON cscart_tag_links.tag_id = cscart_tags.tag_id 
  AND cscart_tag_links.object_id = 36667 
  AND cscart_tag_links.object_type = 'P'

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "0.70"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_tag_links",
          "access_type": "ref",
          "possible_keys": [
            "PRIMARY",
            "tag_id",
            "ids",
            "idx_tag_links_object_id"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "object_type",
            "object_id"
          ],
          "key_length": "7",
          "ref": [
            "const",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "0.25",
            "eval_cost": "0.10",
            "prefix_cost": "0.35",
            "data_read_per_join": "16"
          },
          "used_columns": [
            "tag_id",
            "object_type",
            "object_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "cscart_tags",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "tag_id"
          ],
          "key_length": "3",
          "ref": [
            "cscart_db.cscart_tag_links.tag_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 1,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.25",
            "eval_cost": "0.10",
            "prefix_cost": "0.70",
            "data_read_per_join": "784"
          },
          "used_columns": [
            "tag_id",
            "tag"
          ]
        }
      }
    ]
  }
}