At 10.24am UTC, a redirection issue caused some images not to load. The requests which failed had previously been processed, cached, then purged from the cache as part of a cleanup process. New requests for those images should cause NGINX to invalidate its cache and request image reprocessing. Due to recent NGINX configuration changes, the cache did not invalidate correctly and reprocessing requests were not sent, causing an error "The page isn't redirecting properly". The issue was resolved at 10.59am UTC by mass purging cache entries for all cleaned processed images.
During the period, the majority of requests were successfully returned.
To prevent the issue from reoccurring, additional tests are being implemented for NGINX configuration changes. Additional monitoring alerts are also being designed, for faster issue detection.