SELECT 
  category_id 
FROM 
  cscart_wk_reffer_category_status 
WHERE 
  1 
  AND category_id = "319" 
  AND status = "off"

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_wk_reffer_category_status",
          "access_type": "ALL",
          "rows": 5,
          "filtered": 100,
          "attached_condition": "cscart_wk_reffer_category_status.category_id = '319' and cscart_wk_reffer_category_status.`status` = 'off'"
        }
      }
    ]
  }
}