Examkin

Question

Difficulty: MediumDeployment Strategies

A developer is designing a deployment strategy for a high-traffic web application hosted on Amazon EC2 instances. The company requires a canary deployment strategy where 10%10\% of the production traffic is routed to the new version of the application for validation. The rollout must allow for an immediate rollback to the stable version in the event of an application error, without waiting for client DNS caches to expire.

Which approach should the developer implement to meet these requirements?

  1. A
    Configure Amazon Route 53 with a Weighted routing policy pointing to separate load balancers for the stable and new versions, assigning weights of 9090 and 1010 respectively.
  2. B
    Configure Amazon Route 53 with a Multivalue Answer routing policy to return the IP addresses of both the stable and new instances, letting client-side routing distribute the traffic.
  3. Configure an Application Load Balancer (ALB) with a single listener and two target groups (one for the stable version and one for the new version). Set the listener routing rule to distribute traffic with a weight of 90%90\% to the stable target group and 10%10\% to the new target group.Answer
  4. D
    Configure an Application Load Balancer (ALB) with path-based routing rules to direct 10%10\% of the incoming request paths to the target group of the new version.

Answer

Configure an Application Load Balancer (ALB) with a single listener and two target groups (one for the stable version and one for the new version). Set the listener routing rule to distribute traffic with a weight of 90%90\% to the stable target group and 10%10\% to the new target group.
Configuring an Application Load Balancer (ALB) with weighted target groups shifts traffic at the application layer (HTTP/HTTPS). The client resolves a single DNS name for the load balancer, which then determines how to route requests. When a rollback is required, changing the listener rule weight immediately routes all traffic to the stable target group. This occurs instantly at the ALB level, bypassing client-side DNS caching and TTL limitations.

Step-by-Step Solution

1
Analyze the requirement for a canary deployment that routes 10%10\% of traffic to the new version.
The solution must support weighted routing where 90%90\% goes to the stable version and 10%10\% to the new version.
This establishes the target traffic split for validation.
2
Analyze the constraint regarding immediate rollback without waiting for client DNS caches to expire.
DNS-level routing options (such as Route 53 Weighted routing) are disqualified due to DNS cache TTL latencies.
If an error occurs, client browsers that have cached the DNS record pointing to the canary version will continue to send traffic to it, violating the immediate rollback constraint.
3
Select the application-layer routing mechanism that bypasses DNS cache latency.
An Application Load Balancer (ALB) with weighted target groups distributes traffic at the HTTP layer.
Because the client connects to the same ALB DNS name, updating the listener rule to route 100%100\% of traffic back to the stable target group instantly redirects all subsequent requests without any DNS propagation delay.

Key Concept

Application Load Balancer weighted target groups shift traffic at the HTTP layer, bypassing DNS caching limitations during canary deployments.
Rate this question

Topics

Deployment Strategies

More questions from this topic