Incident with multiple GitHub services

What happened

On April 23, 2026, between 16:03 UTC and 17:27 UTC, multiple GitHub services experienced elevated error rates and degraded performance due to DNS resolution failures originating from our DNS infrastructure in our VA3 datacenter. Approximately 5–7% of overall traffic was affected during the impact window: - Webhooks: ~0.35% of API requests returned 5xx (peak ~0.39%). ~0.88% of requests exceeded 3s latency; at peak, >3s responses represented ~10% of Webhooks API traffic. - Copilot Metrics: ~9% of Copilot Insights dashboard requests returned 5xx. - Copilot cloud agents: ~10% of cloud agent sessions were affected and failing. - Octoshift: 0.88% of active repo migrations failed and 79% saw elevated durations (avg. 5.2 min) during this period. - Git Operations: averaged 1.25% errors over the duration of the incident, with a peak of 2.07% errors. - Actions: Workflow run status updates experienced delays of up to ~8s over the duration of the incident window. Our DNS infrastructure in VA3 entered a degraded state and began intermittently returning NXDOMAIN responses and timing out on lookups for both internal service discovery and external endpoints. This caused a cascading impact ac

1. Resolved · Apr 23, 17:30 UTC
   On April 23, 2026, between 16:03 UTC and 17:27 UTC, multiple GitHub services experienced elevated error rates and degraded performance due to DNS resolution failures originating from our DNS infrastructure in our VA3 datacenter. Approximately 5–7% of overall traffic was affected during the impact window: - Webhooks: ~0.35% of API requests returned 5xx (peak ~0.39%). ~0.88% of requests exceeded 3s latency; at peak, >3s responses represented ~10% of Webhooks API traffic. - Copilot Metrics: ~9% of Copilot Insights dashboard requests returned 5xx. - Copilot cloud agents: ~10% of cloud agent sessions were affected and failing. - Octoshift: 0.88% of active repo migrations failed and 79% saw elevated durations (avg. 5.2 min) during this period. - Git Operations: averaged 1.25% errors over the duration of the incident, with a peak of 2.07% errors. - Actions: Workflow run status updates experienced delays of up to ~8s over the duration of the incident window. Our DNS infrastructure in VA3 entered a degraded state and began intermittently returning NXDOMAIN responses and timing out on lookups for both internal service discovery and external endpoints. This caused a cascading impact across the dependent services listed above. We identified a specific load pattern under which our DNS resolvers began failing. The evidence points to a recently introduced traffic-balancing mechanism, rolled out progressively to support our growth, as the root cause. We have since reverted this chang