ECS with ALB integration in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Architecture

intermediate

ECS Service and ALB Target Group Association

You have an ECS service running tasks behind an Application Load Balancer (ALB). Which configuration ensures that the ALB correctly routes traffic to the ECS tasks?

A Set the ALB listener to forward traffic to the ECS cluster ARN.

B Configure the ECS service to use the ALB target group by specifying the target group ARN in the service's load balancer settings.

C Manually add the EC2 instances running ECS tasks as targets in the ALB target group.

D Register the ECS service's task definition directly as a target in the ALB target group.

💡 Hint

Think about how ECS integrates with ALB to manage dynamic task IPs.

The ECS service must be configured with the ALB target group ARN so that ECS can automatically register and deregister task IPs with the ALB target group. This enables proper routing of traffic to running tasks.

❓ service_behavior

intermediate

Health Check Behavior in ECS with ALB

When using an ALB with ECS, what happens if a task fails the ALB health check?

A The ALB stops sending traffic to the task, but ECS does not replace the task automatically.

B The ECS service scales down the number of tasks to reduce load.

C The ALB redirects traffic to a default target group until the task recovers.

D The ECS service automatically stops and replaces the unhealthy task to maintain the desired count.

💡 Hint

Consider how ECS maintains service availability with unhealthy tasks.

If a task fails the ALB health check, ECS marks it unhealthy and replaces it to keep the desired number of healthy tasks running.

❓ security

advanced

Securing ECS Tasks Behind ALB

You want to ensure that only traffic from your ALB can reach your ECS tasks. Which security group configuration achieves this?

A Assign the same security group to both ALB and ECS tasks allowing all inbound traffic.

B Assign a security group to ECS tasks that allows inbound traffic from 0.0.0.0/0 on the task port.

C Assign a security group to ECS tasks that allows inbound traffic from the ALB's security group only.

D Assign a security group to ECS tasks that allows inbound traffic from the ECS cluster's security group.

💡 Hint

Think about how security groups reference each other to restrict traffic.

By allowing inbound traffic on ECS tasks only from the ALB's security group, you ensure that only the ALB can send traffic to the tasks, enhancing security.

❓ Configuration

advanced

Configuring ECS Service with ALB Listener Rules

You have multiple ECS services behind one ALB. How do you configure the ALB to route requests to the correct ECS service?

A Use ALB listener rules with path-based routing to forward requests to different target groups for each ECS service.

B Assign the same target group to all ECS services and use ECS task definitions to differentiate traffic.

C Create separate ALB listeners for each ECS service on different ports.

D Use DNS round-robin to distribute traffic evenly among ECS services.

💡 Hint

Consider how ALB can route traffic based on URL paths.

ALB listener rules can route traffic based on URL paths to different target groups, each associated with a different ECS service, enabling multiple services behind one ALB.

✅ Best Practice

expert

Optimizing ECS with ALB for High Availability

To maximize availability and fault tolerance for an ECS service behind an ALB, which setup is best?

A Deploy ECS tasks across multiple Availability Zones and enable ALB cross-zone load balancing.

B Deploy ECS tasks in a single Availability Zone and configure ALB with cross-zone load balancing disabled.

C Deploy ECS tasks in multiple regions and use a Network Load Balancer instead of ALB.

D Deploy ECS tasks in a single Availability Zone and use ALB with sticky sessions enabled.

💡 Hint

Think about spreading risk and balancing traffic evenly.

Deploying ECS tasks across multiple Availability Zones and enabling ALB cross-zone load balancing ensures traffic is evenly distributed and service remains available if one zone fails.