SELECT 
  product_variant, 
  category_variants 
FROM 
  cscart_ec_vendor_filter_map

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "3.06"
    },
    "table": {
      "table_name": "cscart_ec_vendor_filter_map",
      "access_type": "ALL",
      "rows_examined_per_scan": 5,
      "rows_produced_per_join": 5,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "2.06",
        "eval_cost": "1.00",
        "prefix_cost": "3.06",
        "data_read_per_join": "80"
      },
      "used_columns": [
        "product_variant",
        "category_variants"
      ]
    }
  }
}