NGINX already has an API to modify servers without restarting NGINX called on-the-fly reconfiguration. However these changes were only made to be temporary and wouldn't survive reboots or restarts. To remedy this we had to rely on configuration templates and restarting NGINX for each change, which isn’t reliable if scaling operations—especially if changes are done repeatedly throughout each day. With NGINX's R8 release, the API stores that state of the reconfigurations in a service registry so that the state can be retrieved from the on disc version--thus making it persistent if the nginx configuration is reloaded.
This will have enormous implications on system monitoring and gives more power to sysadmins who need to make quick changes during peaks and spikes in network traffic. For information on NGINX reconfigurations check out this blog post, or even better, register for an Advanced training class with NGINX University, where you will gain practical knowledge on how to use this technique and more!