As containerization becomes increasingly popular, Azure offers multiple services for running containers. Two key services often cause confusion: Azure Container Instances (ACI) and Azure Container Apps (ACA). Let’s explore when to use each.

Azure Container Instances (ACI)

ACI is Azure’s simplest container hosting service, perfect for scenarios where you need to run containers without managing the underlying infrastructure.

Key Features

  • Serverless containers: No VM management required
  • Per-second billing: Pay only for what you use
  • Quick startup: Containers start in seconds
  • Windows and Linux: Support for both container types

Best Use Cases

  • Batch jobs and data processing
  • CI/CD build agents
  • Development and testing environments
  • Simple web applications with minimal scaling needs
# Example ACI deployment
apiVersion: 2021-03-01
location: East US
name: simple-web-app
properties:
  containers:
  - name: web-app
    properties:
      image: nginx:latest
      resources:
        requests:
          cpu: 1
          memoryInGb: 1.5
      ports:
      - port: 80
  osType: Linux
  restartPolicy: Always

Azure Container Apps (ACA)

ACA is a more sophisticated platform built on Kubernetes, offering advanced features like auto-scaling, traffic splitting, and Dapr integration.

Key Features

  • Kubernetes-based: Built on proven orchestration technology
  • Auto-scaling: Scale to zero and scale based on demand
  • Traffic splitting: Blue-green and canary deployments
  • Dapr integration: Microservices building blocks
  • Event-driven scaling: Scale based on external events

Best Use Cases

  • Microservices architectures
  • API applications requiring auto-scaling
  • Event-driven applications
  • Applications needing advanced deployment strategies
# Example Container Apps deployment
apiVersion: apps/v1
kind: ContainerApp
metadata:
  name: api-service
spec:
  managedEnvironmentId: /subscriptions/.../managedEnvironments/my-env
  configuration:
    activeRevisionsMode: Single
    ingress:
      external: true
      targetPort: 8080
  template:
    containers:
    - image: myapi:latest
      name: api-service
      resources:
        cpu: 0.5
        memory: 1Gi
    scale:
      minReplicas: 0
      maxReplicas: 10
      rules:
      - name: http-scaling
        http:
          metadata:
            concurrentRequests: '10'

Decision Matrix

Feature ACI ACA
Complexity Simple Moderate
Auto-scaling Manual Automatic
Cost (low traffic) Lower Higher
Microservices Limited Excellent
Event-driven Basic Advanced
Networking Basic Advanced

Pricing Considerations

  • ACI: Pay per vCPU and memory per second
  • ACA: Pay for vCPU and memory consumption plus environment costs

Migration Path

Start with ACI for simple use cases, then migrate to ACA as your requirements grow:

  1. Prototype with ACI
  2. Identify scaling and networking needs
  3. Migrate to ACA for production workloads
  4. Leverage advanced ACA features

Conclusion

Choose ACI for simplicity and cost-effectiveness with basic containerized applications. Opt for ACA when you need enterprise-grade features, auto-scaling, and microservices capabilities.

What container service are you using in Azure? Share your experiences and use cases!