Kubernetes

Kubernetes (K8s) is the open source system that runs containers across a fleet of machines. You declare what should be running (“three copies of the API, one of the worker”), and Kubernetes schedules them, restarts anything that dies, scales replicas up and down, and routes traffic between them.

In plain terms

If a container is a shipping container, Kubernetes is the port authority: it decides which ship carries what, replaces lost cargo, and adds ships when traffic surges. A team running 30 microservices does not place each one on a server by hand; Kubernetes does the placement continuously. The managed versions are Amazon EKS, Azure Kubernetes Service (AKS), and Google Kubernetes Engine (GKE), which run the control plane for you. Almost nobody should self-host it.

Why it matters when you migrate

• It’s the portable option at scale. The same manifests run on EKS, AKS, or GKE with modest changes, which keeps a multi-service platform from being welded to one vendor.
• It’s frequently premature. Kubernetes carries real operational weight, and a handful of services runs more cheaply on simpler container platforms like Cloud Run, Fargate, or Container Apps. Containerize first; adopt Kubernetes when the service count or team size demands it, not before.
• It changes how scaling works. Autoscaling happens at two layers, pods and nodes, which is powerful once tuned and a common source of surprise bills until it is.