SELECT 
  bundle_id, 
  linked_promotion_id 
FROM 
  cscart_product_bundles

Query time 0.00059

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.0119958,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_bundles",
          "access_type": "ALL",
          "loops": 1,
          "rows": 7,
          "cost": 0.0119958,
          "filtered": 100
        }
      }
    ]
  }
}