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S3 One Zone-Infrequent Access

20% cheaper than Standard-IA by storing data in a single Availability Zone — a calculated risk that's free money for regenerable data (thumbnails, dev copies, secondary caches) and a terrible idea for anything else.

Last reviewed: July 11, 2026

Prefer step by step? Take the guided S3 One Zone-Infrequent Access walkthrough — free, anonymous, interactive.Have an AI assistant? Jump to the copy-paste audit prompt at the bottom of this sheet.

TL;DR: One Zone-IA stores data in a single AZ instead of three, for 20% less than Standard-IA ($0.01/GB-month) with the same millisecond access. If that AZ is catastrophically lost, so is the data — which is fine, by design, for data you can rebuild or already have elsewhere: thumbnails, transcodes, dev/test copies, secondary caches. The class is a precision tool; the discipline is having a recovery story before you use it.

The numbers

  • Storage: ~$0.01/GB-month vs $0.0125 (Standard-IA) and $0.023 (Standard)
  • Retrieval: ~$0.01/GB, same as Standard-IA; access is millisecond (this is not Glacier)
  • Minimums: 30-day storage duration
  • Availability: 99.5% SLA vs 99.9% for Standard-IA; durability is 11 nines within the zone — but an AZ-wide loss is a data-loss event

At 100 TB of infrequent data: $2,300 (Standard) vs $1,250 (Standard-IA) vs $1,000/month (One Zone-IA). At petabyte scale the delta turns six-figure annually.

Do this

  1. Inventory what's regenerable. The test: if this vanished, is recovery a batch job or a business event? Thumbnails and transcodes (rebuild from originals), replication destinations, dev/test copies of prod data, cache layers over Glacier-archived primaries.

  2. Route it there via lifecycle rules or at upload:

    aws s3 cp ./thumbs/ s3://YOUR-BUCKET/thumbs/ --recursive \
  --storage-class ONEZONE_IA

    or a lifecycle transition ("StorageClass":"ONEZONE_IA") for aging derivative data. S3 Batch Operations reclassifies millions of existing objects in one job.

  3. Tag the intent: criticality:low, backed-up-by:originals-bucket — so future-you and your auditor know why it's single-AZ.

  4. Do the reverse audit too: anything already in One Zone-IA that's actually a sole critical copy is a latent incident. That finding matters more than the savings.

Gotchas

  • Durability ≠ availability. The 11-nines figure covers disk failures within the zone; it does not cover the zone itself. AZ-level events are rare but real (US-East-1 2011, 2017, 2021).
  • "Unknown importance" defaults to safer classes. If nobody can say whether the data is regenerable, it isn't — treat it as critical until proven otherwise.
  • Frequent access breaks the math — retrieval fees stack; genuinely hot data is cheaper in Standard.
  • Importance drifts. The disposable dataset from two years ago may be load-bearing now; review annually.

Skip this if

  • It's the only copy of anything you'd miss — that's what multi-AZ classes and cross-region replication are for.
  • Compliance cares about your availability SLA, not just durability.
  • Your backup posture is thin. Fix durability first; One Zone-IA is a downstream optimization for teams that already have somewhere to restore from.

Run this audit with your AI assistant

Paste this into Claude, ChatGPT, or any agent that can run the AWS CLI with read-only credentials. It audits your account for exactly the waste this sheet describes — and changes nothing.

You are auditing an AWS account for safe S3 One Zone-IA opportunities.
Use the AWS CLI with READ-ONLY credentials. Do not create, modify, or
delete anything — report findings and recommended (unapplied) fixes only.

1. Per bucket: GB per storage class (CloudWatch BucketSizeBytes by
   StorageType), replication config (aws s3api get-bucket-replication),
   versioning, and tags.
2. ONEZONE_IA candidates = data that is BOTH infrequently accessed AND
   provably recoverable from elsewhere:
   - derivative assets (thumbnails/, resized/, transcodes/, previews/)
   - buckets that are replication DESTINATIONS (primary lives elsewhere)
   - dev/test copies of production data
   Never recommend it for sole copies, compliance data, or anything
   whose recoverability you cannot demonstrate from config — list those
   explicitly as "needs human confirmation of a rebuild path".
3. Reverse check: anything ALREADY in ONEZONE_IA that looks like a sole
   critical copy (no replication source, compliance-ish tags/names) —
   flag as a risk finding, arguably more important than the savings.
4. Math: Standard $0.023/GB-mo, Standard-IA $0.0125, One Zone-IA $0.01;
   retrieval ~$0.01/GB on both IA classes; 30-day minimum duration.

Report: candidates table (bucket/prefix | size | why it's regenerable |
est. $/mo saving), risk table (One Zone-IA data with no visible recovery
path), and lifecycle-rule JSON for the safe wins — but do NOT apply
anything.
Works with any assistant that can run shell commands.

Want the guided version?

The S3 One Zone-Infrequent Access walkthrough covers this topic interactively — it asks about your setup, branches to what’s relevant, and quizzes you on the tricky parts. Free and anonymous.

Start the walkthrough

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