Thank you guys. My connections number is quite stable around 200 this year. But the guest number these days suddenly incresed to roughly 400. Previously Guest number is no more than 200. If there is something wrong, I think it should be Guest's number.
BTW, I just updated to v1.18.6. Before I updated, I never saw so high Guest number. But I am not sure if it is because of tue upgrade. My website works well except this.
Alright, after I restart the nodebb real quick, Guest number decrease to 150. I dont know why.