Cases13 cases

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1. IL-0438 Builder Work became almost entirely unreachable with 504 errors when the Amazon CloudFront VPC Origins feature failed

   ANDPAD2026

   Symptoms

   At about 17:00 JST on Thursday 16 July 2026, Datadog alerted, and at almost the same time 5xx errors began to rise on the Amazon CloudFront distributions that used VPC Origins connections. Builder Work, ANDPAD's job and career service for the construction industry, became almost entirely unreachable.

   Service outageHigh error rate

   Trigger

   The Amazon CloudFront VPC Origins feature failed; AWS Health later reported a capacity constraint in an internal shared subsystem that manages connections for VPC Origins.

   Root cause

   Cloud provider outage

   Component

   CDN and edge networkCloud load balancerIngress controllerWeb application firewall rules

   Contributing factor

   Single point of failure

   Detection

   Datadog raised an alert, and at about the same time 5xx errors were seen rising on the CloudFront distributions that used VPC Origins.

   Remediation

   • Decided to route traffic temporarily through an internet-facing ALB without CloudFront
   • Recreated the internet-facing Ingress, attached it to the Argo Rollouts Rollout resource and promoted it
   • Created a regional WAF for the ALB with the security team
   • Created a new IngressClass with the ACM certificate, the WAF and access log settings
   • Added Ingresses for normal traffic, the admin screens and redirects, which restored routing

   Action items

   • Return to the CloudFront and VPC Origins layout while keeping a way to switch to internet-facing in code
   • Keep the internet-facing ALB, limited to approved CIDRs through spec.inboundCIDRs in IngressClassParams, so commenting out securityGroupInboundCidrs in values.yaml opens it to 0.0.0.0/0
   • Point the Terraform-managed Route53 A record back to CloudFront and keep the ALB alias commented out in code, so uncommenting and applying switches DNS to the ALB

   Lessons

   VPC Origins keeps the ALB off the internet and simplifies the traffic path, but it makes the service depend on an AWS-managed shared subsystem, and when that fails the service stops even though CloudFront is healthy. ANDPAD kept VPC Origins and instead prepared the escape route ahead of time, accepting the cost of an ALB that always runs, because recreating the Ingress and attaching it to the Rollout had taken so long during this incident.

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2. IL-0405 An expired AWS Load Balancer Controller webhook certificate left no healthy targets and took BSEE SaaS down

   PortSwigger2026

   Symptoms

   From 10:00 UTC on 11 January 2026 every BSEE SaaS instance in PortSwigger's US and Canada regions was unavailable: customers could not open the Web UI or start scans. The platform team learned of it only when customers reported it through support at 09:52 UTC the next day.

   Service outageTLS certificate errors

   Trigger

   The upgrade of the AWS Load Balancer Controller from v1.14.1 to v1.16.0 on 28 November 2025 left an orphaned webhook TLS secret that cert-manager could not renew, and the certificate in it expired on 8 January 2026.

   Root cause

   Breaking change in an upgrade

   Component

   Ingress controllerAdmission webhookcert-managerHelmConfigMaps and SecretsCloud load balancer

   Contributing factor

   Change with a delayed effectMonitoring blind spot

   Detection

   Customers reported the outage through support at 09:52 UTC on 12 January 2026, almost 24 hours after impact began, and the platform team began investigating at 10:00 UTC.

   Remediation

   • Deleted the orphaned aws-load-balancer-tls secrets in the US and Canada clusters
   • Redeployed the AWS Load Balancer Controller configuration with Helm
   • Verified that new certificates were generated and the webhooks worked again

   Action items

   • Audit all clusters for orphaned secrets that have no owning Certificate resource and resolve them
   • Add high-level application access alerting for each SaaS cluster from an external probe

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3. IL-0188 Rolling updates on EKS returned 502 errors for about 30 seconds because Kubernetes deleted old pods as soon as new pods passed readiness, before the ALB had marked the new pod targets healthy

   Yonghyun Kim2025

   Symptoms

   Every rolling update of the team's microservices on Amazon EKS, behind an Application Load Balancer, was followed by intermittent 502 and 503 errors for users. A Slack message at 3 a.m. read "배포는 성공했는데, 서비스는 죽었다" (the deployment succeeded, but the service died). Every pod was Ready and Datadog was green while users saw errors.

   High error rateService outage

   Trigger

   A rolling update of a Deployment served through an ALB that registers pod IPs as targets, with no pod readiness gates.

   Root cause

   Faulty deployment

   Component

   Cloud load balancerIngress controllerPod termination

   Contributing factor

   Unverified assumptionUnreviewed defaultsMonitoring blind spot

   Detection

   A Slack message at 3 a.m. reported that the deployment had succeeded but the service was down; Datadog dashboards were green at the time.

   Remediation

   • labelled the namespace with elbv2.k8s.aws/pod-readiness-gate-inject=enabled so the AWS Load Balancer Controller injects pod readiness gates and Kubernetes waits for the ALB target to be healthy before deleting old pods

   Lessons

   A pod being Ready in Kubernetes does not mean the load balancer will send it traffic. Without a readiness gate, a rolling update can delete the old pods while the ALB still considers the new targets unhealthy, and dashboards that track pod status stay green during the errors. Making pods wait longer on shutdown reduced the errors but did not fix the start-up gap and made every deployment much slower; the readiness gate ties the pod's Ready state to the ALB's view of the target.

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4. IL-0079 A GKE node auto-upgrade to an ubuntu_containerd image with a kernel regression left kube-proxy unable to apply its ip6tables rules, so load balancer health checks failed and several clusters lost all ingress traffic

   Altinity2025

   Symptoms

   On a Saturday, an OpsGenie alert fired for a ClickHouse cluster in Altinity.Cloud that had gone silent: no queries, no metrics, and no logs from customers trying to connect. The pods were running and the nodes looked healthy, but no traffic reached the database. Other clusters soon showed the same thing, and external access was blocked across several GKE clusters.

   Service outage

   Trigger

   GKE automatically upgraded worker nodes to the ubuntu_containerd image 1.32.3-gke.1785003, which ships kernel 6.8.0-1022-gke.

   Root cause

   Breaking change in an upgrade

   Component

   kube-proxyNode operating system imageLinux kernelCloud load balancer

   Contributing factor

   Unpatched known bugNo staged rollout

   Detection

   An OpsGenie alert fired when one ClickHouse cluster stopped receiving queries, metrics and customer connection logs.

   Remediation

   • added maintenance exceptions to pause all upgrades on the GKE clusters that were not yet affected
   • changed the load balancer health check policy to ignore failed kube-proxy health checks, so traffic flowed to the nodes again
   • began migrating the affected clusters from the ubuntu_containerd to the cos_containerd node image by recreating nodes

   Action items

   • Expand image pre-testing pipelines to catch regressions earlier
   • Enable notifications for upcoming GKE auto-upgrades
   • Make GKE maintenance windows required across the fleet to control when upgrades roll out
   • Track Google's issue and wait for a patched Ubuntu image

   Lessons

   A managed node upgrade can break kube-proxy in a way that leaves pods and nodes looking healthy while the load balancer sends nothing, because the load balancer health check depends on kube-proxy. kube-proxy's own logs showed the cause. Altinity recommends that GKE users on ubuntu_containerd restore traffic by switching to externalTrafficPolicy: Cluster, which disables the kube-proxy health check in the load balancer, move production workloads to cos_containerd, and pause auto-upgrades where possible until a patched image has been confirmed and tested.

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5. IL-0192 A Crossplane composition merge-policy change for a TLS policy update switched Kubernetes Services from LoadBalancer to ClusterIP and deleted the load balancers behind about 25% of Grafana Cloud services

   Grafana Labs2025

   Symptoms

   At 08:41 UTC on 18 February 2025, several Grafana Labs application teams noticed that some of their endpoints were no longer available. The investigation quickly found that the load balancers for those endpoints were gone.

   Service outageResources deleted

   Trigger

   A change to the merge policy of a Crossplane composition, made so that the default TLS policy of the load balancers could be overridden, was applied to development, staging and production at the same time.

   Root cause

   Configuration change

   Component

   Configuration templatingCloud load balancer

   Contributing factor

   Unverified assumptionNo staged rolloutExcessive blast radiusNo safeguard on destructive change

   Detection

   Application teams noticed at 08:41 UTC that some of their endpoints were no longer available.

   Remediation

   • rolled back the Crossplane composition change
   • recreated the affected Kubernetes Services so that Kubernetes recreated their load balancers

   Action items

   • Add a CI check that blocks a deployment to more than one wave, so any exception to the dev, staging, canary, production order is caught
   • Give higher priority to a more sophisticated wave design that was already under discussion
   • Enable deletion protection on the load balancers, one layer below Crossplane
   • Enable deletion protection on other critical cloud provider resources
   • Develop the Crossplane Managed Resources exporter for change validation and visibility, now in beta testing within Platform engineering; simulated against the change that caused this outage, it shows a clear diff
   • Complete and test support for reconfiguring the TLS policy so application teams can deploy it

   Lessons

   A change that looked small and low-risk had a side effect that only a full end-to-end test through Crossplane and the cloud provider's load balancer controller would have shown; seeing the intended override work was not that test. Staged rollout and blast-radius limits that exist only as process can be skipped, so Grafana Labs moved to enforce waves in CI and to add deletion protection on the load balancers themselves, beneath the Crossplane layer.

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