For AWS LB healthchecks, we recommend the following path off the API:
/healthcheck
This route hands back a 200 if the API server is healthy. It determines whether it is healthy by checking a few statistics such as the amount of free memory, the amount of free disk space, network connectivity, file handle usage, CPU utilization and more. If it returns a non-200, then that serves as a signal that the server is in some sort of degraded state and should be rolled over (which elastic scaling groups will accomplish automatically).
In addition to the response status code, the route also hands back some JSON with a few of these statistics so that you can use this endpoint as a means of system monitoring.