Understanding Kubernetes: Part 4-ReplicaSets

Kubernetes replicasets

If you’ve been following our Kubernetes series 2025, welcome back! For new readers, check out Part 3: Understanding Kubernetes: Part 3 -Pod

What is a ReplicaSet in Kubernetes?

A ReplicaSet in Kubernetes ensures that a specified number of identical pod replicas are running at any given time. It provides self-healing capabilities by maintaining the desired state of pods, replacing any that fail or are deleted unexpectedly.

For example:

If you have a backend service and need three instances running for load balancing and high availability, you can define a ReplicaSet to manage those instances. The ReplicaSet ensures that exactly three pods are running. If a pod is deleted, the ReplicaSet immediately creates a new one to maintain the desired count.

ReplicaSet Capabilities:

• Pod Scaling: Adjust the number of replicas to match workload requirements.

• Self-healing: Automatically replaces failed pods.

• Selector Matching: Ensures ReplicaSet only manages pods that match its selector labels.

In my previous role:

As a Senior DevOps Engineer, I used ReplicaSets to manage a Redis-based caching layer. We needed four Redis pods for one use case to ensure consistent high-traffic performance. The ReplicaSet maintained these pods across nodes in the cluster, ensuring availability even during node failures. Additionally, I used a combination of ReplicaSets and node affinity rules to optimize resource allocation, reducing latency for our cache-intensive operations.

Here’s a simple YAML for deploying a ReplicaSet:

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: redis-replicaset
spec:
  replicas: 4
  selector:
    matchLabels:
      app: redis
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
      - name: redis
        image: redis:6.2
        ports:
        - containerPort: 6379

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