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1What are the different types of storage classes in S3?
2What is the S3 Storage Class Analysis feature?
3How to move objects between storage classes?
4What are the use cases of a single-zone IA storage class?
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04 / 04

What are the use cases of a single-zone IA storage class?

S3 One Zone-IA is designed for infrequently accessed data that is easily re-creatable or has secondary copies elsewhere, offering 20% cost savings over Standard-IA by storing data in a single Availability Zone.

S3 One Zone-Infrequent Access (One Zone-IA) is a storage class for data accessed less frequently but needing rapid access when required. Unlike other S3 classes that store data across a minimum of three Availability Zones (AZs), One Zone-IA stores data in a single AZ, making it 20% less expensive than S3 Standard-IA [citation:1][citation:2]. However, this cost savings comes with the trade-off that data will be lost in the event of an AZ destruction, as it is not resilient to such failures [citation:2][citation:3].

Secondary Backup Copies
  1. 1

    Store secondary backup copies of on-premises data where the primary backup exists elsewhere [citation:1][citation:3][citation:10]

  2. 2

    Ideal for backups that are already replicated to another AWS Region for compliance or disaster recovery purposes [citation:1][citation:10]

  3. 3

    Example: Nearmap uses One Zone-IA for a large portion of their stored aerial imagery data, supporting their continued growth [citation:10]

Easily Re-creatable Data
  1. 1

    Store data that can be regenerated from original sources, such as thumbnail images created from original photos [citation:3][citation:7][citation:9]

  2. 2

    Example: An application processing user-uploaded images into thumbnails can store those thumbnails in One Zone-IA since they can be recreated from the original images if lost [citation:7]

  3. 3

    Example: Keepsafe Photo Vault uses One Zone-IA for backup data, as copies of the data exist on mobile or desktop clients [citation:10]

Cross-Region Replication Targets
  1. 1

    Use as a cost-effective target for S3 Cross-Region Replication from another AWS Region [citation:2][citation:3]

  2. 2

    Data replicated to another region already has its primary copy, making single-AZ storage acceptable for the secondary copy [citation:1][citation:10]

  1. 1

    AZ Failure Risk: Data stored in One Zone-IA will be permanently lost in the event of an Availability Zone destruction [citation:2][citation:3][citation:7]

  2. 2

    Not for Primary/Only Copies: Should not be used for data that cannot be recreated or for which no other copy exists [citation:7]

  3. 3

    Minimum Storage Duration: 30-day minimum retention period applies [citation:3][citation:7][citation:8]

  4. 4

    Minimum Object Size: 128 KB minimum object size [citation:3][citation:8]

  5. 5

    Availability SLA: Designed for 99.5% availability, lower than Standard-IA's 99.9% [citation:2][citation:7]

One Zone-IA is not suitable for primary data storage, critical application data, or the only copy of important information. For example, application logs that are stored only in S3 and not backed up elsewhere should use Standard-IA instead of One Zone-IA to ensure availability [citation:7]. The critical factor is whether data loss in a single AZ would be acceptable—if the answer is no, choose Standard-IA or S3 Standard instead [citation:2].

Difficulty: 5/10
Topics: cost optimization, durability, data lifecycle

Scenario Questions

0-2 years experience
  1. 1

    We need to store nightly backup logs that are rarely read. Which S3 storage class would you choose and why?

  2. 2

    If you configure a bucket to use Single‑Zone IA for objects over 5 GB, what happens when a user accesses one of those objects frequently?

  3. 3

    How would you copy an existing object into Single‑Zone IA using the AWS CLI?

2-5 years experience
  1. 1

    Your team’s storage bill is rising for a bucket of archival data. Walk me through how you’d evaluate moving those objects to Single‑Zone IA and what you’d monitor.

  2. 2

    A lifecycle rule that should transition objects to Single‑Zone IA isn’t working. How would you debug the issue?

  3. 3

    Compare Standard‑IA and Single‑Zone IA for a compliance backup that must survive an AZ outage. What trade‑offs do you consider?

5-8 years experience
  1. 1

    Design a multi‑region backup solution that uses Single‑Zone IA to cut costs while still meeting a 99.999999999% durability SLA. How do you address the durability gap?

  2. 2

    At petabyte scale you notice occasional read‑latency spikes for objects stored in Single‑Zone IA. What could be causing this and how would you fix it?

  3. 3

    When defining a lifecycle policy for massive log data, how do you decide which prefixes go to Single‑Zone IA versus Glacier, considering access patterns and cost?

8+ years experience
  1. 1

    Your organization wants a unified storage strategy across dozens of services. Propose an architecture that leverages Single‑Zone IA where appropriate, and outline governance, monitoring, and migration plans.

  2. 2

    How would you build a business case to adopt Single‑Zone IA for certain workloads, balancing cost savings against durability and regulatory constraints?

  3. 3

    In a long‑term roadmap, how do you plan to migrate data out of Single‑Zone IA to newer classes or cross‑region replication without service disruption?

Follow-up Questions

  • ❓What metrics would you watch after moving data to Single‑Zone IA?
  • ❓How would you mitigate the reduced durability risk?
  • ❓What would you do if access patterns suddenly become frequent?