Incident with Pull Requests: High percentage of 500s

Final update

On Monday March 31st, 2026, between 13:53 UTC and 21:23 UTC the Pull Requests service experienced elevated latency and failures. On average, the error rate was 0.15% and peaked at 0.28% of requests to the service. This was due to a change in garbage collection (GC) settings for a Go-based internal service that provides access to Git repository data. The changes caused more frequent GC activity and elevated CPU consumption on a subset of storage nodes, increasing latency and failure rates for some internal API operations. We mitigated the incident by reverting the GC changes. To prevent future incidents and improve time to detection and mitigation, we are instrumenting additional metrics and alerting for GC-related behavior, improving our visibility into other signals that could cause degraded impact of this type, and updating our best practices and standards for garbage collection in Go-based services.

1. Resolved · Mar 31, 21:23 UTC
   On Monday March 31st, 2026, between 13:53 UTC and 21:23 UTC the Pull Requests service experienced elevated latency and failures. On average, the error rate was 0.15% and peaked at 0.28% of requests to the service. This was due to a change in garbage collection (GC) settings for a Go-based internal service that provides access to Git repository data. The changes caused more frequent GC activity and elevated CPU consumption on a subset of storage nodes, increasing latency and failure rates for some internal API operations. We mitigated the incident by reverting the GC changes. To prevent future incidents and improve time to detection and mitigation, we are instrumenting additional metrics and alerting for GC-related behavior, improving our visibility into other signals that could cause degraded impact of this type, and updating our best practices and standards for garbage collection in Go-based services.