a server can return 200 OK to every health check query and 5xx to every production request, is that server up or down? hopefully clear it is down

similarly, if it returns 5xx to every health check query but 200 to every prod request, is it up or down? hopefully clear it is up

if you want to monitor the status of a server (or application) for internal purposes, that's fine, but that's (at best) supplementary signal for the decisions made by a load balancer, not something you can make load balancing decisions on in isolation