Challenges & cheat sheets

Hands-on challenges to sharpen your skills and quick-reference cheat sheets for the tools you use every day.

§1Engineering challenges

01beginnerKubernetes

Debug a CrashLoopBackOff

A pod is stuck in CrashLoopBackOff. The container is running a Python Flask app on port 8080 but the Deployment specifies containerPort 80. Find and fix the issue.

Show hint →

Check the Deployment spec and compare the containerPort with what the app actually listens on.

02intermediateTerraform

Fix a broken Terraform state

A team member manually deleted an S3 bucket that Terraform manages. Running terraform plan now shows it wants to create a new bucket with the same name. Fix the state without destroying other resources.

Show hint →

Look at terraform state rm and terraform import — one removes the broken reference, the other re-imports the real resource.

03intermediatePostgreSQL

Slow PostgreSQL query

A query joining users and orders is taking 2.3 seconds on a table with 500k rows. EXPLAIN shows a sequential scan on the orders table. The WHERE clause filters on created_at. Fix it.

Show hint →

A well-chosen index on the filtered column transforms a sequential scan into an index scan.

04advancedKubernetes

Zero-downtime K8s upgrade

You need to upgrade an EKS cluster from 1.28 to 1.30 with zero downtime. There are 15 services running across 3 node groups. Describe your approach including pre-checks, node group rotation, and rollback plan.

Show hint →

Think about PodDisruptionBudgets, node group versioning, and how to validate each step before proceeding.

More challenges coming weekly. Got one to suggest? Get in touch →

§2kubectl cheat sheet

kubectl get pods -AList all pods in all namespaces

kubectl get pods -n <ns> -o widePods with node and IP info

kubectl describe pod <name>Detailed pod info and events

kubectl logs <pod> -fStream pod logs

kubectl logs <pod> -c <container>Logs from specific container

kubectl exec -it <pod> -- /bin/shShell into a running pod

kubectl apply -f <file>.yamlApply a manifest

kubectl delete -f <file>.yamlDelete resources from manifest

kubectl rollout status deploy/<name>Watch a rollout

kubectl rollout undo deploy/<name>Rollback a deployment

kubectl scale deploy/<name> --replicas=3Scale a deployment

kubectl top pods -ACPU and memory usage per pod

kubectl get events --sort-by=.lastTimestampRecent cluster events

kubectl port-forward svc/<svc> 8080:80Forward a service port locally

kubectl drain <node> --ignore-daemonsetsSafely drain a node

kubectl cordon <node>Mark node as unschedulable

kubectl get nodes -o wideNode list with IPs and roles

kubectl get secret <name> -o jsonpath='{.data.*}' | base64 -dDecode a secret value

§3Terraform cheat sheet

terraform initInitialize working directory

terraform planShow execution plan

terraform plan -out=tfplanSave plan to file

terraform apply tfplanApply a saved plan

terraform apply -auto-approveApply without confirmation

terraform destroyDestroy all managed infrastructure

terraform fmt -recursiveFormat all .tf files

terraform validateValidate configuration syntax

terraform state listList all resources in state

terraform state show <resource>Show details of a state resource

terraform state rm <resource>Remove resource from state (not cloud)

terraform import <resource> <id>Import existing resource into state

terraform outputShow output values

terraform workspace listList workspaces

terraform workspace new <name>Create a new workspace

terraform taint <resource>Mark resource for recreation

terraform graph | dot -Tpng > graph.pngVisualize dependency graph

§4AWS CLI cheat sheet

aws sts get-caller-identityShow current IAM identity

aws configure listShow active credentials and region

aws ec2 describe-instances --query "Reservations[].Instances[].[InstanceId,State.Name,Tags[?Key=='Name'].Value|[0]]" --output table

List EC2 instances as table

aws s3 ls s3://<bucket> --recursive --human-readableList S3 bucket contents

aws s3 sync ./local s3://<bucket>/Sync local folder to S3

aws eks update-kubeconfig --name <cluster> --region <region>Add EKS cluster to kubeconfig

aws logs tail <log-group> --followStream CloudWatch logs

aws ssm start-session --target <instance-id>SSM session without SSH

aws iam list-attached-user-policies --user-name <user>List policies for IAM user

aws secretsmanager get-secret-value --secret-id <name>Retrieve a secret

aws rds describe-db-instances --query "DBInstances[].[DBInstanceIdentifier,DBInstanceStatus]" --output tableList RDS instances

aws cloudformation describe-stacks --query "Stacks[].StackName"List CloudFormation stacks