Timeouts and Latency
184 incident problems that show up as “Timeouts and Latency”.
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When the ConfigMap changed but the Pod keeps using the old valuesAn InfraTree guide that lays out the first signals to check, the CLI verification order, common misdiagnoses, and a safe recovery path when values don't refresh after a ConfigMap update because of envFrom, subPath, volume projection, or rollout trigger differences.Kubernetes3 min readWhen CoreDNS is Running but only DNS lookups failAn InfraTree guide that lays out the first signals to check, the CLI verification order, common misdiagnoses, and a safe recovery path when the CoreDNS Pod looks healthy but failures occur in the kube-dns path, upstream, node-local-dns, or policy.Kubernetes3 min readWhat to check first when CrashLoopBackOff appearsAn InfraTree guide that lays out the first signals to check, the CLI verification order, common misdiagnoses, and a safe recovery path when a Pod restarts repeatedly and the real cause is left in the previous logs and events.Kubernetes3 min read
Recommended problems
Reviewed problems first, then problems with detailed scenarios.
Docker build cache not used: npm ci reruns even when only the README changedDocker build cache not used: npm ci reruns even is a hands-on troubleshooting drill. Order Dockerfile steps so the dependency layer stays cached. build-cache-hygiene needs to be checked by narrowing scope, recent change, and the current live signal before rollback. 실무에서는 build...ReviewedCI/CDBeginner3 minFreenpm ci fails with EUSAGE: only the PR that edited package.jsonnpm ci fails with EUSAGE: only the PR that edited package.json is a hands-on troubleshooting drill. Fix the lock file when npm ci refuses to install. ci-cd-workflow-debugging needs to be checked by narrowing scope, recent change, and the current live signal before rollback. 실무...ReviewedCI/CDBeginner3 minFreeLoad average is 40 but the CPU is mostly idle: I/O waitLoad average is 40 but the CPU is mostly idle: I/O wait is a hands-on troubleshooting drill. Separate CPU saturation from I/O wait when load average spikes. linux-performance-and-observability needs to be checked by narrowing scope, recent change, and the current live signal b...ReviewedLinuxIntermediate16 minFreeNETWORK-027Resolver search suffix turns short name into wrong destinationResolver search suffix turns short name into wrong destination is a hands-on troubleshooting drill. A short hostname works in one environment and points somewhere else in another because search suffix order changed. DNS and Routing needs to be checked by narrowing scope, recen...ReviewedNetworkBeginner13 minFreeNETWORK-064ACL shadow rule blocks load balancer health checks from the SNAT poolUser traffic seems permitted on paper, but backends stay marked unhealthy because the firewall never allowed the translated health-check source range.ReviewedNetworkIntermediate18 minFree504 Gateway Timeout: a slow export endpoint behind a 60-second proxy timeout504 Gateway Timeout: a slow export endpoint behind a 60-second proxy timeout is a hands-on troubleshooting drill. Match the proxy timeout with how long the upstream actually takes, and fix long requests properly. Network Services And Operations needs to be checked by narrowing...ReviewedNetworkIntermediate16 minFree
All problems (184)
npm ci fails with EUSAGE: only the PR that edited package.jsonnpm ci fails with EUSAGE: only the PR that edited package.json is a hands-on troubleshooting drill. Fix the lock file when npm ci refuses to install. ci-cd-workflow-debugging needs to be checked by narrowing scope, recent change, and the current live signal before rollback. 실무...ReviewedCI/CDBeginner3 minFreeConnection refused vs connection timed out: what is the difference?Connection refused vs connection timed out: what is the difference? is a hands-on troubleshooting drill. Use the kind of connect error to decide where the connection stopped. Network Services And Operations needs to be checked by narrowing scope, recent change, and the current...ReviewedNetworkBeginner3 minFreeCORS error: No 'Access-Control-Allow-Origin' header is presentCORS error: No 'Access-Control-Allow-Origin' header is present is a hands-on troubleshooting drill. Read the most common CORS error and decide which side has to change. WAF and AppSec Controls needs to be checked by narrowing scope, recent change, and the current live signal b...ReviewedSecurityBeginner3 minFreeDocker build cache not used: npm ci reruns even when only the README changedDocker build cache not used: npm ci reruns even is a hands-on troubleshooting drill. Order Dockerfile steps so the dependency layer stays cached. build-cache-hygiene needs to be checked by narrowing scope, recent change, and the current live signal before rollback. 실무에서는 build...ReviewedCI/CDBeginner3 minFree504 Gateway Timeout: only the order list fails after a table migration504 Gateway Timeout: only the order list fails is a hands-on troubleshooting drill. A 504 means the upstream answered too slowly; find out why. NGINX Network Services And Operations needs to be checked by narrowing scope, recent change, and the current live signal before rollb...ReviewedNetworkBeginner3 minFreePort times out only from outside: it works on the server itselfPort times out only from outside: it works on the server itself is a hands-on troubleshooting drill. When a port works locally but times out remotely, check the firewall. firewall-policy-basics needs to be checked by narrowing scope, recent change, and the current live signal...ReviewedNetworkBeginner3 minFreeNETWORK-064ACL shadow rule blocks load balancer health checks from the SNAT poolUser traffic seems permitted on paper, but backends stay marked unhealthy because the firewall never allowed the translated health-check source range.ReviewedNetworkIntermediate18 minFreeSECURITY-033Managed WAF rule blocks a legitimate JSON admin requestThe API works for most clients, but a large or nested admin payload trips a managed protection rule and looks like an application bug at first glance.ReviewedSecurityIntermediate20 minFreeSECURITY-001The SSH management path is blocked after an overly narrow allowlist changeA situation where the access-control policy looks correct, but one jump-host range is missing, so the actual operations management path is blocked.ReviewedSecurityBeginner16 minFreeNETWORK-027Resolver search suffix turns short name into wrong destinationResolver search suffix turns short name into wrong destination is a hands-on troubleshooting drill. A short hostname works in one environment and points somewhere else in another because search suffix order changed. DNS and Routing needs to be checked by narrowing scope, recen...ReviewedNetworkBeginner13 minFreeLoad average is 40 but the CPU is mostly idle: I/O waitLoad average is 40 but the CPU is mostly idle: I/O wait is a hands-on troubleshooting drill. Separate CPU saturation from I/O wait when load average spikes. linux-performance-and-observability needs to be checked by narrowing scope, recent change, and the current live signal b...ReviewedLinuxIntermediate16 minFree504 Gateway Timeout: a slow export endpoint behind a 60-second proxy timeout504 Gateway Timeout: a slow export endpoint behind a 60-second proxy timeout is a hands-on troubleshooting drill. Match the proxy timeout with how long the upstream actually takes, and fix long requests properly. Network Services And Operations needs to be checked by narrowing...ReviewedNetworkIntermediate16 minFreeNETWORK-072LACP bundle never forms after a stack replacementCabling is correct, but the upstream sees a different partner identity and refuses to aggregate the links into the expected bundle.NetworkIntermediate16 minFreeNETWORK-068Port-channel min-links keeps the bundle down after a partial member failureOne physical path still forwards traffic, but the logical interface remains down because the configured minimum bundle size is no longer satisfied.NetworkIntermediate17 minFreeNETWORK-084Spanning-tree guard blocks one hypervisor uplinkThe network configuration is stable, but a host starts sending unexpected bridge protocol units and the protection feature shuts the access port down.NetworkIntermediate17 minFreeSECURITY-082TLS offload proxy re-encrypts with a deprecated cipher set and only one partner API rejects itClient-facing certificates look modern, but one partner integration breaks because the upstream re-encryption profile still uses a weaker legacy policy.SecurityIntermediate17 minFreeCICD-056CloudFront invalidation runs before the new asset manifest is fully publishedThe deployment pipeline clears the CDN correctly, but users still receive broken bundles because the invalidation precedes the final asset upload and manifest sync.CI/CDIntermediate18 minFreeNETWORK-080MAC flapping alarms appearThe network is stable, but one mobile workload triggers MAC move alarms and intermittent forwarding loss because the switching design assumes slower host movement.NetworkIntermediate18 minFreeCICD-030Release note generation fails on shallow clone runnersRelease note generation fails on shallow clone runners is a hands-on troubleshooting drill. A changelog step depends on full git history, but shallow checkout settings hide the required tags and commits. GitHub GitHub Actions Workflows needs to be checked by narrowing scope, r...CI/CDIntermediate18 minFreeNETWORK-037Internal clients cannot reach the public VIPExternal users can access the service normally, but inside clients fail when they resolve the same public name because the edge path does not support loopback NAT.NetworkIntermediate20 minFree