Cases15 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-0463 Secure Connect connectors timed out after a GKE control plane upgrade left Harness's internal load balancer unreachable

   Harness2026

   Symptoms

   On 12 May 2026, Harness customers who used Secure Connect saw git connector tests fail with connection timeouts and CI pipelines hang or fail, while connectors without Secure Connect kept working. Continuous Integration Enterprise Mac and Linux Cloud Builds in Prod 1, Prod 2 and Prod 3 were affected.

   Network unreachableResources deleted

   Trigger

   An automated GKE control plane upgrade on the cluster that hosts Harness's internal Secure Connect FRPS (Fast Reverse Proxy Server) infrastructure.

   Root cause

   Cloud provider outage

   Component

   GKE control planeCloud controller managerCloud load balancer

   Contributing factor

   –

   Remediation

   • Ran a rollout restart of the FRPS deployment, which restored client connectivity to FRPS but not the lost IP
   • Deleted and recreated the internal service frps-internal so GKE provisioned a new load balancer and IP
   • Updated the Cloud DNS A record to the new load balancer IP

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3. IL-0542 Twingate authentication and authorization requests failed at higher rates after traffic moved onto a smaller GKE cluster

   Twingate2025

   Symptoms

   On 21 March 2025, between 21:10 and 21:41 UTC, part of the authentication and authorization requests to Twingate services failed with elevated error rates.

   High error rate

   Trigger

   Twingate saw anomalies in one of its GKE clusters and scaled down the deployments in that cluster to protect the rest of the system, which moved its traffic to the other clusters.

   Root cause

   Cloud provider outage

   Component

   Cloud load balancerGKE control planeHorizontal pod autoscalerCluster autoscaler

   Contributing factor

   Retry stormNo headroomOverlapping failuresHarmful manual action

   Detection

   Twingate observed anomalies in one of its GKE clusters at the start of the incident.

   Remediation

   • Reintroduced capacity in the cluster that had been scaled down, so traffic was rebalanced across regions

   Action items

   • Keep working with the cloud provider to find the cause of the unexpected timeouts and of the cluster update's impact
   • Run deployments in all regions with the same number of replicas in the HPA configuration
   • Raise the maximum node counts of the cluster node autoscalers to leave more room to scale up
   • Configure the HPA to scale up faster

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4. IL-0119 ChatGPT web service pods crash-looped on failing health checks after a Cosmos DB failure, leaving too few healthy pods to serve the web layer

   OpenAI2025

   Symptoms

   From 3:30am to 7:08am PT, chatgpt.com and a small number of OpenAI APIs returned elevated error rates. The status page classed the incident as a full outage.

   High error rateContainer crash loopProbe failures

   Trigger

   A failure of Cosmos DB in ChatGPT, at OpenAI's service provider.

   Root cause

   Cloud provider outage

   Component

   Database

   Contributing factor

   Health check tied to a dependency

   Remediation

   • the service provider recovered the affected Cosmos DB databases at 4:25am PT
   • fixed the web server's health checking logic, which ended the pod crash loop

   Action items

   • Change the web systems to degrade more gracefully when they fail, including concurrency control and better load shedding
   • Make the database layer more resilient to service provider outages (described as already underway)

   Lessons

   The database came back at 4:25am PT, yet users saw errors until 7:08am PT: the web tier's own health checks kept removing pods after the dependency had recovered. The planned changes target the web tier's behaviour under failure, with concurrency control and load shedding, rather than the database alone.

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5. IL-0084 Packet drops on a bare metal provider's vSwitch forced Namespace to rebuild its fra3 region and left global capacity short, and the next day slow NVMe writes on a control plane node drove the Kubernetes API server to very high CPU

   Namespace2024

   Symptoms

   From 17 October 2024, packets through the vSwitch that joined Namespace's bare metal machines at one provider in the fra3 region were dropped at random. Retries in TCP, QUIC and the Namespace control plane hid most of it, but the SLO error budget for latency targets on key interactions began to burn.

   Intermittent connection failuresHigh latencyControl plane lagService outage

   Trigger

   Random packet drops on the bare metal provider's vSwitch from 17 October 2024; for the second outage, a rate of Kubernetes changes that the slow NVMe on one control plane node could no longer keep up with.

   Root cause

   Cloud provider outage

   Component

   Kubernetes API server

   Contributing factor

   No capacity planningNo headroomOverlapping failures

   Detection

   SLO-based monitoring of latency targets showed the error budget burning while retries hid the individual packet drops.

   Remediation

   • diverted all customer traffic from fra3 to other regions
   • connected each provider machine to the zrh1 cluster over Wireguard instead of the vSwitch
   • repaved every fra3 machine with a new identity, certificates and encryption-at-rest keys, dropping regional caches to recover faster
   • cloned existing datasets in a more distributed way to speed up repaving the machines
   • added machines back to the new region in batches and returned the region to the compute pool
   • redirected workloads away from zrh1 during the second outage
   • cloned the failing control plane node's key state to a higher-capacity node that took over its role and IP address

   Action items

   • Credit all instances that ran during the outages back to customers
   • Build up backup regions and solutions so a similar event has options that do not affect customers

   Lessons

   Running hot with a delayed hardware delivery left no room to take a region out, so fixing a provider network fault turned into a global capacity shortage. After one outage the team was anchored on its cause and first looked for network problems in the second outage, which had a different cause: a control plane node whose disk could not keep up with the Kubernetes change rate.

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