SELECT 
  object_id, 
  thread_id, 
  type, 
  object_type 
FROM 
  cscart_discussion 
WHERE 
  1 
  AND object_id = 146 
  AND object_type = 'P'

Query time 0.00045

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "3.43"
    },
    "table": {
      "table_name": "cscart_discussion",
      "access_type": "ALL",
      "rows_examined_per_scan": 29,
      "rows_produced_per_join": 0,
      "filtered": "3.45",
      "cost_info": {
        "read_cost": "3.33",
        "eval_cost": "0.10",
        "prefix_cost": "3.43",
        "data_read_per_join": "23"
      },
      "used_columns": [
        "thread_id",
        "object_id",
        "object_type",
        "type"
      ],
      "attached_condition": "((`mobikul_delivery_boy_livedemo`.`cscart_discussion`.`object_id` = 146) and (`mobikul_delivery_boy_livedemo`.`cscart_discussion`.`object_type` = 'P'))"
    }
  }
}