Helm
Package a chart, change values, and let the release manage the objects.
Playgrounds · free
Sixteen sandboxes you can actually use.
Every card below is a graded sandbox that runs in your browser: real objects in a simulated cluster, checked against state rather than terminal output. No account, no cluster to pay for, no session that expires mid-command.
They are simulations, and we say so: you learn the API and the failure modes, not a live kubelet. When you want real infrastructure, the free third-party options are listed underneath — clearly labelled, because they are not ours.
Kubernetes, extended
Ingress
Route a host to a Service, with TLS terminated at a secret.
NetworkPolicy
Deny by default, then allow one peer — the policyAPI, not a firewall note.
Horizontal Pod Autoscaler
Scale a Deployment between 1 and 4 replicas on CPU utilisation.
KServe
Declare an InferenceService with a model format, storage URI and runtime.
Argo CD / GitOps
Register an application and sync the cluster to the repository.
Observability and security
Prometheus
Write scrape configs and an alerting rule with a real `for:` duration.
Grafana
Build the dashboard the alert links to, from the metrics you scrape.
Logs
Find the failing request id in a seeded log, then fix the service.
Image scanning
Read a Trivy report, rebuild the image, and prove the finding is gone.
Secret hygiene
Move a key out of the repository, ignore the env file, lock it to 600.
AI, without a model key
MCP, end to end
Register a server, define a tool schema, and write the call/refuse transcript.
LangGraph
A typed state, two nodes, and START → retrieve → answer → END.
Retrieval (RAG)
Index a corpus, retrieve the policy, and cite the file it came from.
Containers
Dockerfile to container
Build an image, expose a port, run it detached and publish it.
Compose stack
A web and database stack with its own network and named volume.
When you want a real cluster
These are free tiers run by other people. They need an account, they rate-limit, and they can change their terms — none of which is under our control. We list them because a week on a real cluster teaches things a simulation cannot.
- Killercoda
Real Linux, Kubernetes and Docker sandboxes in the browser. Free tier with session limits; no credit card.
- Play with Kubernetes
A free four-hour multi-node cluster per session from Docker. No account needed; you build the cluster yourself.
- Oracle Cloud Always Free
ARM compute that is free indefinitely — enough for a real k3s cluster. Account approval and capacity are the catch.
- GitHub Codespaces
60 free hours a month on a personal account; runs kind or k3d inside the devcontainer.
- kind (local)
Not a hosted sandbox: a single-node cluster on your own machine, free forever. Best once the labs feel small.
For context: a commercial playground charges because each tile is a live cluster, billed by the hour. We do not pretend to match that for free — we grade the API surface, and point you at someone else’s free tier for the rest.
New to the topic? Read the lesson first — or browse the full catalog.