What is pods?
A pod is the smallest unit you can run in Kubernetes. It’s a group of one or more containers that are tightly coupled, sharing the same network address, storage volumes, and configuration. Think of a pod as a wrapper that holds containers together so they can work as a single, cohesive application component.
Let's break it down
- Containers inside a pod: Usually there’s just one container, but you can put a side‑car container (like a logger) alongside the main one.
- Shared network: All containers in the pod use the same IP address and port space, so they can talk to each other via localhost.
- Shared storage: Volumes attached to the pod are visible to every container inside it.
- Lifecycle: Pods are created, scheduled to a node, run, and then are terminated as a whole. If a pod dies, Kubernetes creates a new one to replace it.
Why does it matter?
Pods give you a simple way to manage containers that need to work together. By bundling them, you avoid complex networking setups, ensure they start and stop together, and let Kubernetes handle placement, scaling, and health‑checking for the whole group as a single entity.
Where is it used?
- In any Kubernetes cluster, whether on‑premises, in the cloud (AWS EKS, Google GKE, Azure AKS), or in a local development setup (Minikube, Kind).
- For micro‑service architectures where each service runs in its own pod.
- For side‑car patterns such as logging agents, proxies, or monitoring tools that run alongside the main app container.
- In batch jobs or cron jobs that need a short‑lived execution environment.
Good things about it
- Simplicity: You treat a group of containers as one unit, making deployment easier.
- Co‑location: Containers that need to share data or communicate quickly are placed together.
- Resource sharing: Shared network and storage reduce configuration overhead.
- Kubernetes integration: Pods work seamlessly with scheduling, scaling, rolling updates, and health checks.
- Flexibility: You can add side‑car containers without changing the main application image.
Not-so-good things
- Node limitation: All containers in a pod run on the same physical node, so they can’t be spread across multiple machines.
- Ephemeral nature: Pods are meant to be replaceable; storing state inside a pod without persistent volumes can lead to data loss.
- Complexity at scale: Managing thousands of tiny pods can become overwhelming without proper tooling.
- Networking constraints: Since pods share an IP, you can’t expose each container on a different port without extra configuration.
- Resource over‑allocation: If you bundle many containers in one pod, you may waste CPU or memory if they don’t all need it simultaneously.