Recently at my workplace, a new application using Node JS and NextJS was implemented. As with all our public facing websites, it was placed behind Azure’s Front Door service, to provide web application firewall (WAF) and caching functionality.
During testing, it was discovered that the site would sometimes not render properly. However it wasn’t a 100% failure rate.
An Early Theory – Geography
Early on a common theme was noticed. If the user device was located in Brisbane, regardless of OS, browser or ISP used, the site would fail to render. If the device was in or close to Sydney, it would render properly. Trying a few other geographical points using VPNs showed similar behaviours.