Minimal Downtime DR with Auto Scaling and DynamoDB Global Tables

SAA-C03 By islever Editorial Last updated

Design highly available and/or fault-tolerant architectures.

Short answer

A Create an Auto Scaling group and an ELB in the DR Region, configure DynamoDB as a global table, and use DNS failover for minimal downtime.

Question

A company hosts its application in the AWS Cloud. The application runs on Amazon EC2 instances in an Auto Scaling group behind an Elastic Load Balancing (ELB) load balancer. The application connects to an Amazon DynamoDB table. For disaster recovery (DR) purposes, the company wants to ensure that the application is available from another AWS Region with minimal downtime. Which solution will meet these requirements with the LEAST downtime?
  1. Create an Auto Scaling group and an ELB in the DR Region. Configure the DynamoDB table as a global table. Configure DNS failover to point to the new DR Region's ELB. Correct Answer
  2. Create an AWS CloudFormation template to create EC2 instances, ELBs, and DynamoDB tables to be launched when necessary. Configure DNS failover to point to the new DR Region's ELB.
  3. Create an AWS CloudFormation template to create EC2 instances and an ELB to be launched when necessary. Configure the DynamoDB table as a global table. Configure DNS failover to point to the new DR Region's ELB.
  4. Create an Auto Scaling group and an ELB in the DR Region. Configure the DynamoDB table as a global table. Create an Amazon CloudWatch alarm with an evaluation period of 10 minutes to invoke an AWS Lambda function that updates Amazon Route 53 to point to the DR Region's ELB.

Key Takeaways

The core concept is pre-warming resources in the DR region versus on-demand provisioning; the common trap is selecting CloudFormation or Lambda-based automation which introduces latency.

This question addresses designing a highly available disaster recovery architecture using AWS Auto Scaling, ELB, and DynamoDB Global Tables to achieve minimal downtime.

Common mistake: Learners often choose Option C because they overlook that CloudFormation stack creation time adds significant delay compared to having an Auto Scaling group already running (even with zero capacity or minimal warm-up) in the DR region.

Expert Analysis

Why the Answer Is Correct

Option A is the correct choice because it establishes a "warm standby" or active-active capable state in the Disaster Recovery (DR) region by pre-creating the compute infrastructure (Auto Scaling Group and ELB). While an ASG might scale from zero, the networking components (ELB) and the application code base are deployed. More importantly, DynamoDB Global Tables provide multi-region replication with automatic failover capabilities at the database layer. By configuring DNS failover (Route 53 health checks) to point to the DR ELB, traffic is routed immediately upon failure detection. This minimizes downtime because the infrastructure is logically present and ready to accept traffic, unlike cold starts.

Why the Other Options Are Wrong

Options B and C rely on AWS CloudFormation to create EC2 instances, ELBs, and potentially DynamoDB tables only when necessary. Provisioning new EC2 instances involves AMI loading, instance launching, and application startup, which can take minutes—far exceeding the definition of "minimal downtime." Option D suggests using a CloudWatch alarm and Lambda to update Route 53. While this automates the DNS switch, it still relies on the underlying infrastructure being ready. If the ASG/ELB isn't pre-provisioned (as implied by the contrast with A), there's a risk of cold start delays. Furthermore, Option A explicitly states the ASG and ELB are created in the DR Region, implying a persistent setup that handles scaling instantly.

Community Comment Notes

The community overwhelmingly supports Option A, citing that pre-existing infrastructure ensures immediate availability. As user 'Scheldon' noted, "at least 1 server and ELB will be waiting," ensuring no boot-time delay. User 'LeonSauveterre' emphasized that "Waiting for the CloudFormation stack... delays recovery," highlighting the critical difference between warm and cold DR strategies. Comments consistently reinforce that minimal downtime requires avoiding the provisioning phase during the failover event.

Exam Strategy

When asked for "minimal downtime" or "high availability" in DR scenarios, always prefer solutions where infrastructure is pre-provisioned (Warm Standby or Active-Passive with pre-warmed instances) over Cold Standby (provision on failure). Evaluate the latency introduced by each step: DNS propagation vs. Instance Boot Time vs. Stack Creation Time.

Frequently Asked Questions

Why is CloudFormation not suitable for minimal downtime?

CloudFormation creates resources on-demand during a disaster event. The time taken to launch EC2 instances, attach volumes, and start applications introduces significant latency, violating the 'minimal downtime' requirement.

Does DynamoDB Global Table handle failover automatically?

DynamoDB Global Tables replicate data across regions with low latency. However, application-level failover (routing traffic via Route 53) must still be configured manually or via automation to direct users to the active region.

More SAA-C03 FAQ →

Community Votes

A
100%

100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 8 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 8

  1. Scheldon 👍 4 Answered A
    AnswerA Hence there is no information that solution need to be cost effective and the main requirement is minimal downtime i would go with AUTOSCALING in DR region with 1 ELB and 1 server there but in case of need amount of servers can be increased automatically. Hence at least 1 server and ELB will be waiting and DynamoDB thanks to global table will be active in the same DR region as well, hence we need to inform users, using DNS about new destination, hence DNS failover to the ELB in DR region is the best solution here.
  2. Alagong 👍 4 Answered A
    Create an Auto Scaling group and an ELB in the DR Region, configuring the DynamoDB table as a global table, and setting up DNS failover to the new ELB. This approach allows for quick failover since the infrastructure is already in place and only DNS needs to be updated to redirect traffic.
  3. muhammadahmer36 👍 4 Answered A
    Downtime I would choose Auto scaling + DNS failover rather than use cloud formation create infrastructure in DR region or Auto scaling + Lambda
  4. Tanidanindo 👍 3 Answered A
    Least downtime. C does not offer minimal downtime
  5. LeonSauveterre 👍 2 Answered A
    A - By creating an Auto Scaling group and ELB in the DR Region upfront, you ensure that the infrastructure is ready to handle traffic immediately in case of a failure in the primary Region. This minimizes downtime during a disaster. B & C - Waiting for the CloudFormation stack to create instances, ELBs, and DynamoDB tables delays recovery. D - CloudWatch alarms and Lambda functions will introduce additional complexity and potential delays due to the evaluation period (>= 10 minutes). For A, simply create an Auto Scaling group and ELB in the DR Region. Use the same configurations as the primary Region. Just make sure that the AMI used for EC2 instances includes all necessary application code and dependencies.
Show 3 more comments
  1. Hkayne 👍 2 Answered A
    With dynamo global tables, we just need to create an ELB and a ASG in the DR region resources. This resources will be used only if the main region fail over.
  2. mk168898 👍 2
    B and C seems to take a while to launch, so it is not minimal down time
  3. Awsbeginner87 👍 2 Answered C
    Option C

Reader comments & corrections

No reader corrections yet — spotted an error or have a note? Share it below.

Log in to comment, report an error, or add a note about this question.

Submitted for moderation before publishing. Keep it helpful and respectful.

S3 Multi-Region Access Point and Replication Strategy

S-grade

Securing NLB with Security Groups for Minimal Change

S-grade

Most Cost-Effective 7-Year Retention for EBS Snapshots?

S-grade

AWS Forecast vs SageMaker for Time-Series Prediction

S-grade

Practice All SAA-C03 Questions

Access 120 questions with complete answers and detailed explanations.

View Full SAA-C03 Practice Test →

← Back to SAA-C03 Study Guide