AWS Certified Solutions Architect - Associate
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A company needs a backup strategy for its three-tier stateless web application. The web application runs on Amazon EC2 instances in an Auto Scaling group with a dynamic scaling policy that is configured to respond to scaling events. The database tier runs on Amazon RDS for PostgreSQL. The web application does not require temporary local storage on the EC2 instances. The company's recovery point objective (RPO) is 2 hours.
The backup strategy must maximize scalability and optimize resource utilization for this environment.
Which solution will meet these requirements?
Other
Community
UAnonymous
A
Take snapshots of Amazon Elastic Block Store (Amazon EBS) volumes of the EC2 instances and database every 2 hours to meet the RPO.
B
Configure a snapshot lifecycle policy to take Amazon Elastic Block Store (Amazon EBS) snapshots. Enable automated backups in Amazon RDS to meet the RPO.
C
Retain the latest Amazon Machine Images (AMIs) of the web and application tiers. Enable automated backups in Amazon RDS and use point-in-time recovery to meet the RPO.
D
Take snapshots of Amazon Elastic Block Store (Amazon EBS) volumes of the EC2 instances every 2 hours. Enable automated backups in Amazon RDS and use point-in-time recovery to meet the RPO.
Explanation:
Explanation
Correct Answer: C
Why Option C is correct:
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Stateless web application: Since the web application is stateless and doesn't require temporary local storage, there's no need to back up EBS volumes of EC2 instances. The application state should be stored elsewhere (like in the database or external storage).
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Auto Scaling group: EC2 instances in an Auto Scaling group are ephemeral and can be terminated/recreated. The proper approach is to use Amazon Machine Images (AMIs) that contain the application code and configuration. When new instances are launched, they use the latest AMI.
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RDS PostgreSQL: For the database tier, RDS automated backups with point-in-time recovery (PITR) provide the required RPO of 2 hours. RDS automated backups are managed by AWS and provide continuous backup capability.
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Scalability and resource optimization: This solution maximizes scalability because:
- AMIs are lightweight (only contain OS and application code)
- No unnecessary EBS snapshots consuming storage
- RDS automated backups are managed by AWS
- Auto Scaling can quickly launch instances from AMIs
Why other options are incorrect:
Option A: Incorrect because:
- Taking EBS snapshots of EC2 instances for stateless applications is wasteful
- RDS snapshots every 2 hours would be manual and inefficient compared to automated backups
- Doesn't leverage AMIs for Auto Scaling
Option B: Incorrect because:
- EBS snapshot lifecycle policy still creates unnecessary snapshots for stateless instances
- Doesn't address the need for AMIs for Auto Scaling
Option D: Incorrect because:
- Taking EBS snapshots every 2 hours for stateless EC2 instances is inefficient
- While RDS automated backups with PITR is correct, the EC2 backup approach is wrong
Key AWS Concepts:
- Stateless applications: Should store state externally; instances can be replaced
- Auto Scaling: Use AMIs for consistent instance launches
- RDS automated backups: Provide continuous backup with PITR capability
- RPO (Recovery Point Objective): Maximum acceptable data loss (2 hours in this case)
This solution optimally balances backup requirements with scalability and resource utilization for the described environment.
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