ECS · Elastic Container Service

Outcome

• Fargate & ALBCluster + Task Definition + Run Task
  • Create a cluster via CLI with Container Insights enabled
  • Push an image to ECR
  • Write a task definition JSON from scratch
  • Run a one-off Fargate task and get its public IP
  • Read stoppedReason and exitCode from a failed task
• Fargate & ALBService + ALB + Rolling Deploy
  • Create an ALB + target group wired to an ECS service
  • Deploy a new task definition revision via update-service
  • Explain minimumHealthyPercent and maximumPercent in a rolling update
  • Trigger the deployment circuit breaker and confirm auto-rollback
• Fargate & ALBIAM Roles + Secrets
  • Create and assign both the execution role and task role
  • Explain exactly what each role does and when it is used
  • Inject a Secrets Manager secret as an environment variable
  • Diagnose a permissions failure by identifying which role is missing the permission
• Fargate & ALBAuto Scaling
  • Register a scalable target and attach a target tracking policy
  • Use hey to generate load and observe tasks scaling out
  • Read scaling activity history from Application Auto Scaling
• Fargate & ALBECS Exec + Observability
  • ECS Exec into a running Fargate task
  • Inspect the credential endpoint at 169.254.170.2 and identify the Task Role
  • Explain why ECS Exec is safer than SSH
• GitHub Actions DeployThe Application + Docker Image
  • Write a Dockerfile with correct layer ordering for cache efficiency
  • Explain why npm ci is used over npm install in a Dockerfile
  • Authenticate Docker to ECR and push an image with a git SHA tag
  • Explain why latest is dangerous in production
• GitHub Actions DeployECS Infrastructure Setup
  • Distinguish between the Task Execution Role and the Task Role
  • Explain why the Task SG sources from the ALB SG instead of 0.0.0.0/0
  • Register a task definition and explain every required field
  • Connect an ALB target group to an ECS service and explain what containerPort maps to
• GitHub Actions DeployGitHub Actions CI/CD Pipeline
  • Write a workflow that builds, tags with $GITHUB_SHA: pushes to ECR, and deploys to ECS
  • Explain why $GITHUB_SHA is used instead of latest
  • Explain why tests must run before the Docker build step
  • Store secrets correctly, never hardcode credentials in workflow YAML
• GitHub Actions DeployRolling Deployment + Rollback
  • Explain minimumHealthyPercent and maximumPercent and their tradeoffs
  • Perform a manual rollback to a previous task definition revision
  • Explain connection draining and tune the deregistration delay
  • Identify a stuck deployment (health check loop) from describe-services output
• GitHub Actions DeployCloudWatch Monitoring + Alarms
  • Name the four key ALB + ECS metrics to watch post-deployment
  • Create alarms for 5xx rate, healthy host count, and CPU with correct thresholds
  • Read container logs and identify startup errors
  • Distinguish a deployment issue (health check loop) from an application issue (5xx post-deployment)