DOP-C02 Resilient Cloud Solutions Practice Question
A company wants to ensure that its Amazon S3 bucket can withstand the loss of an entire AWS Availability Zone. Which configuration meets this requirement?
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
✓
Use the S3 Standard storage class.
S3 Standard storage class automatically replicates data across at least three Availability Zones within an AWS Region, ensuring resilience against the loss of an entire AZ. Option B is incorrect because cross-Region replication replicates data to a different AWS Region, which provides geographic resilience but not specifically AZ resilience within the same Region. Option C is incorrect because S3 Versioning helps protect against accidental deletion or overwrite by preserving previous versions, but it does not provide data replication across AZs. Option D is incorrect because S3 One Zone-IA stores data in a single AZ, which would not withstand the loss of that AZ.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use the S3 Standard storage class.
Why this is correct
S3 Standard is the default storage class and is engineered to deliver 99.999999999% object durability and 99.99% availability by synchronously storing each object across a minimum of three Availability Zones (AZs) within the same AWS Region. When an AZ becomes unavailable, S3 automatically serves requests from the remaining copies, so the bucket stays accessible without manual intervention. Because the data exists in at least three independent AZs, a single AZ failure does not cause data loss or downtime, making it the appropriate choice for resilience against an AZ disruption.
- ✗
Configure cross-Region replication to another bucket.
Why it's wrong here
Cross-Region Replication (CRR) copies objects to a bucket in a different AWS Region, which protects against an entire region becoming unavailable. It does not increase resilience to an AZ failure in the source region, because the source bucket's S3 service already replicates data across multiple AZs within its region. While CRR provides an off-region copy for disaster recovery, it is not needed to survive a single AZ outage and adds cost and complexity compared to simply selecting S3 Standard.
- ✗
Enable S3 Versioning on the bucket.
Why it's wrong here
Amazon S3 Versioning keeps multiple variants of an object whenever it is overwritten or deleted, allowing you to restore previous states or recover from accidental deletions. However, versioning does not change the physical storage locality or redundancy; all versions of an object are still subject to the durability characteristics of the storage class in use. If the underlying bucket uses a storage class that does not replicate across AZs, or if an AZ failure destroys the single copy, all versions are lost. Therefore versioning is a logical data-protection feature, not a solution for infrastructure-level failures like an AZ outage.
- ✗
Use the S3 One Zone-IA storage class.
Why it's wrong here
S3 One Zone-IA (Infrequent Access) stores data only in a single Availability Zone and does not replicate it to other AZs. If that particular AZ experiences an outage or is destroyed, the data is permanently lost, resulting in no availability or durability guarantee beyond the single location. The storage class is designed for cost-effective archiving of easily recreatable or secondary backups, but it is explicitly unsupported for workloads that need resilience to an AZ failure.
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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