Troubleshooting Interview Questions — All Categories
141 questions across 32 categories
Real production incidents, spanning Kubernetes, AWS, Docker, Terraform, CI/CD, networking, and databases — diagnosing a specific symptom back to its actual cause, not textbook definitions.
Two people merged to main within a minute of each other, and now two deployment workflow runs are executing at the same time, racing to deploy. How do you prevent this?
IntermediateGitHub Actions6 min
A required status check on a GitHub branch protection rule is permanently stuck showing "Expected — Waiting for status to be reported", blocking every PR from merging. What's going on?
IntermediateGitHub7 min
An internal tool making GitHub API calls started getting 403 errors, but checking the rate limit endpoint shows plenty of requests remaining. What else could be causing this?
IntermediateGitHub7 min
A CODEOWNERS file lists a team as owner of a directory, but PRs touching that directory aren't automatically requesting review from that team. What's likely misconfigured?
IntermediateGitHub6 min
A security review finds a contractor has write access to a sensitive repository, but nobody remembers explicitly granting it. How did this happen, and how do you audit for it going forward?
IntermediateGitHub6 min
A teammate used 'cache' to pass compiled build output from the build job to the deploy job, and it intermittently fails to find the files. What did they get wrong?
IntermediateGitLab CI/CD6 min
A new job you added to .gitlab-ci.yml is stuck 'pending' forever and never picked up by any runner. What's the most likely cause, and how do you fix it?
BeginnerGitLab CI/CD5 min
What debugging challenge does a GitLab merged results pipeline introduce that a plain branch pipeline doesn't, when a job fails?
IntermediateGitLab CI/CD6 min
A merge request's 'Merge' button is greyed out with the widget stuck on 'Checking if merge request can be merged...' indefinitely, even though the pipeline passed. How do you debug this?
IntermediateGitLab CI/CD6 min
An Argo CD application shows OutOfSync even though the pods running in the cluster look correct and healthy. What would you check?
IntermediateArgo CDKubernetesGitOps8 min
A Helm pre-upgrade hook Job doesn't run before the Deployment update it's supposed to precede — why, and how do you fix the ordering?
AdvancedHelm7 min
A helm rollback succeeds but the application still behaves like the newer version — why might rollback not fully revert the deployed state?
AdvancedHelm7 min
A `helm upgrade` gets interrupted (CI job killed, network blip) and now every subsequent `helm upgrade` or `helm rollback` fails with "another operation (install/upgrade/rollback) is in progress". How do you recover?
IntermediateHelmKubernetes8 min
A Helm chart's deployed values don't match any single values file you can find — how does Helm's value-override precedence actually work?
IntermediateHelmKubernetes6 min
Someone manually changed a cloud resource in the console that's managed by your IaC. What actually happens the next time the pipeline runs, and how would you handle the drift?
IntermediateTerraform8 min
Your Jenkins pipeline runs three test suites in parallel stages. One fails after 2 minutes, but the pipeline keeps running the other two for another 20 minutes before reporting failure. How do you fix this?
IntermediateJenkins6 min
You upgraded a Jenkins plugin to patch a security vulnerability, and now several unrelated pipelines are failing with errors that didn't exist yesterday. How do you handle this?
IntermediateJenkins7 min
A Jenkins pipeline stage runs `docker build`. It works fine when run by hand on the agent, but fails in the pipeline with a permission denied error talking to the Docker daemon. Why?
IntermediateJenkinsDocker8 min
Two mutating webhooks both touch a pod's containers field, and the final result isn't what either webhook intended alone — how do you diagnose and resolve this?
ExpertKubernetes8 min
Every pod creation cluster-wide suddenly starts failing with an admission webhook TLS error — what happened, and how do you recover quickly?
ExpertKubernetes8 min
A validating webhook is rejecting pod creations that look completely valid — how do you diagnose what it's actually objecting to?
AdvancedKubernetes7 min
kubectl apply --dry-run=server behaves unexpectedly for requests a webhook handles — what does a webhook's sideEffects field have to do with it?
AdvancedKubernetes6 min
The API server responds slowly to all requests — how do you determine whether etcd, the API server, or something else is the bottleneck?
ExpertKubernetes9 min
Why might an HPA be unable to scale a Deployment even with plenty of spare CPU capacity on existing nodes?
IntermediateKubernetes6 min