SELECT 
  bundle_id, 
  linked_promotion_id 
FROM 
  cscart_product_bundles

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_bundles",
      "access_type": "ALL",
      "rows": 3,
      "filtered": 100
    }
  }
}