SAA-C03 Design Cost-Optimized Architectures Practice Question
A SaaS company uses an S3 bucket for database backups created daily. Backups are rarely restored; the company’s documented RTO is 24 hours, and the compliance policy requires backups be kept for 90 days. The team currently stores all backups in S3 Standard, which is costly.
Which single lifecycle policy change is most cost-optimized while still meeting the 24-hour RTO and 90-day retention?
⚠ Common exam trap
A common mix-up: candidates choose S3 Glacier Deep Archive for maximum cost savings without verifying that its retrieval time (12–48 hours) can exceed the 24-hour RTO, or they may overlook that S3 Glacier Instant Retrieval is not the most cost-effective option for data that is restored only rarely.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a lifecycle rule to transition backups older than 1 day to S3 Glacier Flexible Retrieval, and keep them until day 90.
S3 Glacier Flexible Retrieval provides retrieval times from minutes to hours, which meets the 24-hour RTO, and offers significant cost savings over S3 Standard for data that is rarely accessed. Transitioning backups older than 1 day to this storage class reduces costs while retaining them for the required 90-day compliance period.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Add a lifecycle rule to transition backups older than 1 day to S3 Glacier Flexible Retrieval, and keep them until day 90.
Why this is correct
This option correctly leverages S3 Lifecycle rules to transition older, less frequently accessed backups to S3 Glacier Flexible Retrieval. This storage class provides significant cost savings compared to S3 Standard or S3-IA, while still supporting retrieval times measured in hours, which comfortably meets a 24-hour Recovery Time Objective (RTO). Maintaining retention until day 90 also satisfies the long-term data retention requirement efficiently.
- ✗
Add a lifecycle rule to transition backups older than 1 day to S3 Glacier Instant Retrieval, and keep them until day 90.
Why it's wrong here
While S3 Glacier Instant Retrieval offers immediate access, meeting the RTO, it is generally a more expensive storage class for data that is infrequently accessed, especially compared to Glacier Flexible Retrieval. For backups that are older than one day and expected to be rarely retrieved, the higher per-GB retrieval cost and storage cost of Instant Retrieval make it less cost-effective. This choice fails to optimize costs effectively when a cheaper alternative with an acceptable RTO exists.
- ✗
Add a lifecycle rule to transition backups older than 1 day to S3 Glacier Deep Archive, and keep them until day 90 with no restore configuration.
Why it's wrong here
S3 Glacier Deep Archive is designed for the lowest-cost archival storage, but its standard retrieval times typically range from 12 to 48 hours, with bulk retrievals taking up to 48 hours. This extended retrieval period directly conflicts with a strict 24-hour Recovery Time Objective (RTO), as there's no guarantee of data availability within the required timeframe. Therefore, despite meeting the 90-day retention, this storage class is unsuitable due to its potentially slow retrieval performance.
- ✗
Add a lifecycle rule to transition backups older than 1 day to S3 One Zone-IA, and delete them after 7 days.
Why it's wrong here
This option is fundamentally flawed because it specifies deleting backups after only 7 days, which directly violates the required 90-day data retention policy. While S3 One Zone-IA offers cost savings by storing data in a single Availability Zone, its primary drawback here is the insufficient retention period. The solution must ensure data is available for the full 90 days, making this lifecycle rule unacceptable.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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