Sandbox

SELECT 
  * 
FROM 
  ushop_wk_delivery_day_settings 
  LEFT JOIN ushop_shippings ON ushop_shippings.shipping_id = ushop_wk_delivery_day_settings.shipping_id 
WHERE 
  1 
  AND ushop_wk_delivery_day_settings.company_id = 0 
  AND ushop_wk_delivery_day_settings.shipping_id = '' 
  AND ushop_shippings.wk_en_delivery_time = 'Y'

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}