I have one windows IIS server to serve my website images and it works good enough . for a part of time, starting from 27 Dec 2023 to 16 Jan 2024, I changed public or valid ip of IIS web server and set it behind nginx web server as a reverse proxy and ssl offloading.
at that moment (27 Dec 2023) average response time of that domain goes higher but after reverting that change, it's not coming back to default old value (which is better and faster) . picture below describe better:
point 1: network change occurred
point 2: network change revert back
temporary change in network related components cause jump in average response time of google search console crawl stats report even after reverting that changes. all other monitoring and logs does not encountered any slowness. I analyzed and checked IIS logs, 3rd party monitoring system and my grafana prometheus blackbox_exporter related metrics. totaly nothing changed! my question is how to resolve this? and what is a cause of this effect?