🔐 Kubernetes Secrets vs. ConfigMaps – Which One and When? (2025 Guide)

In the world of Kubernetes, separating code from configuration is a best practice. But when it comes to managing settings like environment variables, API tokens, and database credentials — you’ll come across two powerful tools:

• ✅ ConfigMaps
• 🔒 Secrets

They both store configuration, but they are NOT the same — and using them interchangeably could lead to security issues or operational headaches.

Let’s break them down — from basics to best practices — and figure out which one to use, when.

---

🧠 What’s the Difference Between a ConfigMap and a Secret?

Feature	ConfigMap	Secret
Purpose	Store non-sensitive config data	Store sensitive data like passwords, tokens
Encoding	Stored in plain text	Stored in base64-encoded format
Access Control	Readable by default	Can be restricted using RBAC
Encryption	Not encrypted at rest	Can be encrypted at rest (KMS or etcd config)
Mounting	As files or env vars	Same (files/env), but secured
Example Use	App name, log level, config toggles	API keys, DB passwords, SSH keys

---

🔧 1. What is a ConfigMap?

ConfigMaps are used to store non-sensitive configuration in a key-value format.

✅ Common Use Cases:

• Application name, port, timezone
• Feature flags
• JSON configs
• External URLs

✍️ Example:

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  APP_NAME: "myapp"
  LOG_LEVEL: "debug"

📦 Usage in Pod:

env:
- name: APP_NAME
  valueFrom:
    configMapKeyRef:
      name: app-config
      key: APP_NAME

---

🔐 2. What is a Secret?

Secrets are used to store sensitive data like passwords, tokens, SSH keys, and TLS certs.

Though they’re base64-encoded by default (⚠️ not encrypted), Kubernetes supports encryption at rest and RBAC to control access.

✅ Common Use Cases:

• DB credentials
• OAuth tokens
• TLS certificates
• Service account keys

✍️ Example:

apiVersion: v1
kind: Secret
metadata:
  name: db-secret
type: Opaque
data:
  DB_PASSWORD: cGFzc3dvcmQxMjM=  # base64 encoded

🔁 echo -n 'password123' | base64 = cGFzc3dvcmQxMjM=

📦 Usage in Pod:

env:
- name: DB_PASSWORD
  valueFrom:
    secretKeyRef:
      name: db-secret
      key: DB_PASSWORD

---

🔐 3. Are Secrets Really Secure?

Yes, if you configure them properly:

Feature	Enabled By
🔒 Encryption at Rest	Set up in EncryptionConfiguration for etcd
✅ RBAC Access Control	Use Role + RoleBinding to restrict access
👁️ Audit Logging	Log access to Secrets
🔄 Automatic Rotation	Use external Secret managers (Vault, AWS Secrets Manager)

⚠️ By default, Secrets are just base64 — not truly secure.
Always combine them with proper encryption, least-privilege access, and rotation practices.

---

🔀 4. How to Choose – ConfigMap or Secret?

Scenario	Use
✅ Application name	ConfigMap
✅ Logging level (debug/info)	ConfigMap
🔐 API token for 3rd-party service	Secret
🔐 Database password	Secret
✅ Feature toggle flags	ConfigMap
🔐 SSL cert/key pair	Secret (TLS type)
✅ External API URL	ConfigMap
🔐 OAuth client secret	Secret

🧠 Rule of Thumb:
If you wouldn’t share the value on a public forum, put it in a Secret.

---

🛠️ 5. Best Practices

✅ ConfigMaps:

• Keep unrelated config keys in separate ConfigMaps.
• Use volumes if you want to mount full configs (e.g., YAML or JSON files).
• Version them using labels or annotations.

✅ Secrets:

• Enable encryption at rest for etcd.
• Store only what is absolutely necessary.
• Integrate with external secret managers like:
  • HashiCorp Vault
  • AWS Secrets Manager
  • Azure Key Vault
• Rotate credentials regularly and use initContainers or sidecars for dynamic secrets.

---

🧩 Bonus: Use Both Together

Yes, you can — and often should — use ConfigMaps and Secrets together in the same pod.

Example:

env:
- name: ENV
  valueFrom:
    configMapKeyRef:
      name: app-config
      key: ENV
- name: DB_PASSWORD
  valueFrom:
    secretKeyRef:
      name: db-secret
      key: DB_PASSWORD

This keeps your sensitive data isolated, while making general configuration easily manageable.

---

💼 Real-World Example: A Web App in K8s

Config Item	Source	Reason
DB_HOST	ConfigMap	Safe to expose
DB_PORT	ConfigMap	Non-sensitive
DB_PASSWORD	Secret	Needs encryption
API_KEY	Secret	Confidential
APP_ENV	ConfigMap	Just toggles
TLS Key/Cert	Secret (TLS type)	Secure by default

---

🧠 Final Thoughts

• Use ConfigMaps for what’s safe to expose
• Use Secrets for anything you’d protect with encryption
• Secure your Secrets with RBAC, encryption, and external managers
• Keep everything version-controlled and auditable

Don’t treat your Kubernetes cluster like a vault.
Treat it like an API-driven operating system, and secure it the same way.

---

Just let me know!