Unusual traffic spike resulting in problems resolving DOIs for a percentage of traffic

At 2025-10-17 03:08Z lasting for a minute or so, there was a surge of resolution traffic at doi.org at maybe 150x normal traffic. We suspect this may have been a DDoS attempt or a test of a possible DDoS technique. Resolution was impacted for ordinary users of doi.org; as many as 80000 resolution requests (approximately 5% of the apparently legitimate traffic during this time) received various errors, most in the first few minutes but some as late as 03:32Z. Currently resolution is normal but we continue to monitor.