WAF : Site path routing and hot standby

HEllo,

 

We have Waf rule configured with site path routing to 4 real servers.

Do you have a recommendation on how to manage a faulty servers. If I understand well, hot standby works for one server with only one backup server?

Can we use hotstandby with 4 servers ? How it will works in this configuration?

 

Thanks for your help.

Max