SELECT 
  bundle_id, 
  linked_promotion_id 
FROM 
  cscart_product_bundles

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "2.89"
    },
    "table": {
      "table_name": "cscart_product_bundles",
      "access_type": "ALL",
      "rows_examined_per_scan": 3,
      "rows_produced_per_join": 3,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "2.29",
        "eval_cost": "0.60",
        "prefix_cost": "2.89",
        "data_read_per_join": "120"
      },
      "used_columns": [
        "bundle_id",
        "linked_promotion_id"
      ]
    }
  }
}