K3s

K3s is Kubernetes that fits in your pocket. A single binary under 70MB, certified Kubernetes, runs on 512MB RAM, supports ARM — it's the de facto standard for edge, IoT, and anywhere full K8s is overkill. CoreDNS, Traefik, and containerd bundled in.

Rancher built this for cattle ranchers running Kubernetes on tractors, and that tells you everything about the design goals. It runs on satellites, factory floors, and retail stores. Compared to full Kubernetes (more features, more resources), K3s is the same API with 90% less overhead. Compared to Nomad (simpler non-K8s orchestration), K3s keeps Kubernetes compatibility. Compared to MicroK8s (Canonical's version), K3s is lighter.

Use this when you need Kubernetes at the edge or on resource-constrained hardware. Also great for local development clusters. Skip this if you need the full K8s feature set with custom schedulers and advanced CRDs.

The catch: some K8s features are stripped or replaced (etcd swapped for SQLite by default, cloud controllers removed). Add-ons you depend on in full K8s may need manual installation. Apache 2.0 license, CNCF sandbox project.