Target groups concept in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Target Group Health Checks

What happens when a target in an AWS target group fails its health check?

A The load balancer stops sending traffic to that target until it passes health checks again.

B The target is permanently removed from the target group and must be re-registered manually.

C The load balancer redirects traffic to the failing target to test recovery.

D The target group automatically scales up to replace the failing target.

💡 Hint

Think about how a load balancer keeps your app healthy by avoiding bad servers.

When a target fails health checks, the load balancer temporarily stops sending traffic to it until it becomes healthy again. It does not remove or replace the target automatically.

❓ Architecture

intermediate

Target Group and Load Balancer Association

Which statement correctly describes how target groups are used with an Application Load Balancer (ALB)?

A Target groups are used only for Network Load Balancers, not ALBs.

B Each target group can only be associated with one ALB at a time.

C An ALB routes incoming traffic to one or more target groups based on listener rules.

D An ALB sends traffic directly to EC2 instances without using target groups.

💡 Hint

Consider how ALB directs traffic based on rules and groups of servers.

Application Load Balancers use listener rules to route traffic to one or more target groups. Target groups contain the registered targets like EC2 instances or IP addresses.

❓ Configuration

advanced

Target Group Health Check Configuration Impact

Given this target group health check configuration:

Health check path: /status
Healthy threshold: 3
Unhealthy threshold: 2
Interval: 10 seconds
Timeout: 5 seconds

What is the minimum time before a target is marked unhealthy after it starts failing health checks?

A 20 seconds

B 10 seconds

C 15 seconds

D 30 seconds

💡 Hint

Calculate using the unhealthy threshold and interval values.

The target must fail 2 consecutive health checks (unhealthy threshold) with checks every 10 seconds (interval). So, 2 x 10 = 20 seconds minimum before marked unhealthy.

❓ security

advanced

Security Group Rules for Target Groups

You have an ALB and a target group with EC2 instances. Which security group rule is necessary for the EC2 instances to receive traffic from the ALB?

A Allow inbound traffic from anywhere on all ports.

B Allow inbound traffic on the target port from the ALB's security group.

C Allow outbound traffic to the ALB's IP addresses.

D Allow inbound traffic only from the internet gateway.

💡 Hint

Think about how security groups reference each other for controlled access.

The EC2 instances must allow inbound traffic on the port used by the target group from the ALB's security group to receive traffic securely.

❓ service_behavior

expert

Target Group Deregistration Delay Effect

An EC2 instance is deregistered from a target group with a deregistration delay of 300 seconds. What happens to in-flight requests during this delay?

A The load balancer sends requests to the instance only if it passes health checks during the delay.

B The load balancer immediately stops sending requests, and in-flight requests are terminated.

C The instance is removed instantly, and traffic is routed to other targets without delay.

D The load balancer stops sending new requests to the instance but allows in-flight requests to complete during the delay.

💡 Hint

Consider how deregistration delay helps graceful shutdown.

Deregistration delay allows the load balancer to stop sending new requests but keeps the instance available to complete existing requests during the delay period.

Practice

1. What is the main purpose of a target group in AWS Elastic Load Balancing?

easy

A. To create virtual private clouds

B. To store user data securely

C. To manage DNS records

D. To group servers for load balancing and health checks

Solution

1. Step 1: Understand target group role

   A target group groups servers (targets) to distribute incoming traffic.

2. Step 2: Identify key functions

   It also performs health checks to ensure traffic goes only to healthy servers.

3. Final Answer:

   To group servers for load balancing and health checks -> Option D

4. Quick Check:

   Target groups = server grouping + health checks [OK]

Hint: Target groups organize servers for load balancing [OK]

Common Mistakes:

• Confusing target groups with security groups
• Thinking target groups store data
• Mixing target groups with VPC functions

2. Which of the following is the correct way to specify a target group protocol in AWS CLI?

easy

A. aws elbv2 create-target-group --protocol HTTP

B. aws elbv2 create-target-group --protocol FTP

C. aws elbv2 create-target-group --protocol SMTP

D. aws elbv2 create-target-group --protocol SSH

Solution

1. Step 1: Recall supported protocols for target groups

   AWS target groups support HTTP, HTTPS, TCP, TLS, UDP, and TCP_UDP protocols.

2. Step 2: Identify valid protocol in options

   HTTP is a valid protocol; FTP, SMTP, and SSH are not supported for target groups.

3. Final Answer:

   aws elbv2 create-target-group --protocol HTTP -> Option A

4. Quick Check:

   HTTP is valid protocol for target groups [OK]

Hint: Use HTTP or HTTPS for target group protocol [OK]

Common Mistakes:

• Using unsupported protocols like FTP or SSH
• Confusing target group protocol with security group rules
• Misspelling protocol names

3. Given a target group with 3 registered targets, two healthy and one unhealthy, how will the load balancer route traffic?

medium

A. It sends traffic only to the two healthy targets

B. It sends traffic equally to all three targets

C. It sends traffic only to the unhealthy target

D. It stops sending traffic until all targets are healthy

Solution

1. Step 1: Understand health check impact

   Load balancers route traffic only to targets marked healthy by health checks.

2. Step 2: Apply to given targets

   With two healthy and one unhealthy, traffic goes only to the two healthy targets.

3. Final Answer:

   It sends traffic only to the two healthy targets -> Option A

4. Quick Check:

   Traffic routes only to healthy targets [OK]

Hint: Load balancer skips unhealthy targets [OK]

Common Mistakes:

• Assuming traffic goes to all targets regardless of health
• Thinking traffic stops if any target is unhealthy
• Confusing unhealthy targets with backup targets

4. You created a target group but your load balancer shows no healthy targets. What is the most likely issue?

medium

A. Load balancer is in a different region

B. Security group blocks health check traffic

C. Targets are not registered with the target group

D. Target group protocol is set to FTP

Solution

1. Step 1: Check common causes for no healthy targets

   Targets not registered or security blocking health checks cause no healthy targets.

2. Step 2: Analyze options

   Security group blocking health check traffic prevents health checks from succeeding, causing targets to be unhealthy.

3. Final Answer:

   Security group blocks health check traffic -> Option B

4. Quick Check:

   Blocked health checks cause no healthy targets [OK]

Hint: Check security groups allow health check ports [OK]

Common Mistakes:

• Ignoring security group rules
• Assuming region mismatch causes health check failure
• Using unsupported protocols like FTP

5. You want to route HTTP traffic to two different target groups based on URL path: /images/* to one group and /api/* to another. Which AWS service feature should you use?

hard

A. Elastic IP addresses assigned to each target group

B. Network Load Balancer with static IP routing

C. Application Load Balancer with path-based routing rules

D. Classic Load Balancer with SSL termination

Solution

1. Step 1: Identify routing needs

   Routing based on URL path requires path-based routing rules.

2. Step 2: Match AWS service feature

   Application Load Balancer supports path-based routing to different target groups.

3. Step 3: Exclude incorrect options

   Network Load Balancer does not support path-based routing; Classic Load Balancer lacks this feature; Elastic IPs do not route traffic by path.

4. Final Answer:

   Application Load Balancer with path-based routing rules -> Option C

5. Quick Check:

   Path-based routing = Application Load Balancer [OK]

Hint: Use ALB for URL path routing to target groups [OK]

Common Mistakes:

• Using Network Load Balancer for path routing
• Confusing Classic Load Balancer features
• Thinking Elastic IPs control routing rules