SELECT 
  conditions 
FROM 
  cscart_promotions 
WHERE 
  status = 'A' 
  AND zone = 'catalog'

Query time 0.00058

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "3.34"
    },
    "table": {
      "table_name": "cscart_promotions",
      "access_type": "index_merge",
      "possible_keys": [
        "status_idx",
        "zone_idx"
      ],
      "key": "intersect(status_idx,zone_idx)",
      "key_length": "3,1",
      "rows_examined_per_scan": 3,
      "rows_produced_per_join": 3,
      "filtered": "79.05",
      "cost_info": {
        "read_cost": "3.04",
        "eval_cost": "0.30",
        "prefix_cost": "3.34",
        "data_read_per_join": "2K"
      },
      "used_columns": [
        "conditions",
        "zone",
        "status"
      ],
      "attached_condition": "((`cscart_db`.`cscart_promotions`.`status` = 'A') and (`cscart_db`.`cscart_promotions`.`zone` = 'catalog'))"
    }
  }
}