Blue-green infrastructure pattern in Terraform - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Architecture

intermediate

Identify the main benefit of the blue-green deployment pattern

Which of the following best describes the primary advantage of using the blue-green deployment pattern in cloud infrastructure?

A It allows zero downtime deployments by switching traffic between two identical environments.

B It reduces cloud costs by using only one environment at a time.

C It automatically scales resources based on traffic load.

D It encrypts all data in transit between environments.

💡 Hint

Think about how traffic is managed during updates.

The blue-green deployment pattern uses two identical environments (blue and green). Traffic switches from one to the other to deploy updates without downtime.

❓ Configuration

intermediate

Terraform snippet for blue-green environment switching

Given two identical AWS ECS services named blue and green, which Terraform snippet correctly switches the production traffic to the green service using an Application Load Balancer listener rule?

Terraform

resource "aws_lb_listener_rule" "green_traffic" {
  listener_arn = aws_lb_listener.front_end.arn
  priority     = 100

  action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.green.arn
  }

  condition {
    path_pattern {
      values = ["/app/*"]
    }
  }
}

A Use aws_lb_listener_rule with action type 'forward' to green target group and priority lower than blue's rule.

B Use aws_lb_listener_rule with action type 'redirect' to green target group and priority higher than blue's rule.

C Use aws_lb_listener_rule with action type 'fixed-response' to green target group and priority equal to blue's rule.

D Use aws_lb_listener_rule with action type 'forward' to green target group and priority higher than blue's rule.

💡 Hint

Higher priority rules take precedence in ALB listener rules.

To switch traffic, the listener rule forwarding to the green target group must have a higher priority than the blue's rule so it takes precedence.

❓ security

advanced

Security considerations in blue-green deployments

Which security risk is most relevant when running both blue and green environments simultaneously in a blue-green deployment?

A Inability to encrypt data in transit between environments.

B Data loss caused by switching traffic between environments.

C Increased attack surface due to both environments being live and accessible.

D Automatic deletion of logs from the inactive environment.

💡 Hint

Think about exposure when two environments are active.

Running two environments simultaneously means both are accessible, increasing the potential attack surface if not properly secured.

✅ Best Practice

advanced

Best practice for database handling in blue-green deployments

In a blue-green deployment, what is the recommended approach to handle database schema changes to avoid downtime?

A Apply backward-compatible schema changes before switching traffic, then clean up old schema after verification.

B Avoid any schema changes during blue-green deployments to prevent conflicts.

C Maintain separate databases for blue and green environments and merge data after deployment.

D Switch traffic first, then apply schema changes directly on the new environment's database.

💡 Hint

Consider how to keep both environments compatible during transition.

Applying backward-compatible schema changes first ensures both environments work with the database, avoiding downtime during traffic switch.

❓ service_behavior

expert

Result of traffic switch in blue-green deployment with sticky sessions

In a blue-green deployment using an Application Load Balancer with sticky sessions enabled, what is the expected behavior immediately after switching traffic from blue to green environment?

A All users are instantly routed to the green environment regardless of existing sessions.

B Existing users continue to be routed to the blue environment until their session expires, new users go to green.

C Sticky sessions are disabled automatically during the switch causing all users to lose session data.

D The load balancer duplicates traffic to both blue and green environments during the switch.

💡 Hint

Sticky sessions bind users to a specific backend until session ends.

Sticky sessions keep users bound to their original environment until the session expires, so existing users stay on blue while new users go to green.