AWS S3 storage classes compared for the exam

Amazon S3 storage classes are a favorite exam topic because they are a table in disguise: the same service, several price and access trade-offs, and a handful of numbers that separate them. The AWS Cloud Practitioner exam sits in the Cloud Technology and Services domain here, the largest at 34%, and questions usually describe a data access pattern and ask you to pick the class.

First, the basics. S3 is object storage: an object is a file plus its metadata, stored in a bucket and identified by a key. You choose a Region when you create a bucket, and you cannot change the bucket's name or Region afterward. Buckets and objects are private by default. S3 is designed for 99.999999999% (11 nines) durability across its storage classes, so the classes differ on availability, number of Availability Zones, cost, minimum storage duration and how fast you can get data back, not on how safe the data is designed to be.

The classes side by side

A dash means this article does not state a figure for that cell.

S3 Express One Zone is a single-AZ class for the most latency-sensitive workloads, with single-digit millisecond access, a 99.95% availability design and directory buckets. Learn its one-line description and move on.

How to tell them apart

• Standard is the default for frequently accessed data.
• Intelligent-Tiering moves objects between access tiers for you. It has no retrieval fees but charges a small per-object monitoring and automation fee. Objects start in Frequent Access, move to Infrequent Access after 30 days without access, and to Archive Instant Access after 90 days. Objects under 128 KB are not auto-tiered and stay in Frequent Access.
• Standard-IA vs One Zone-IA differ in one thing: resilience. One Zone-IA stores data in a single AZ, so it is cheaper but does not survive the loss of that AZ. Standard-IA fits the primary or only copy; One Zone-IA fits data you could re-create. Both charge a per-GB retrieval fee.
• The Glacier classes are the archive tier. Instant Retrieval can be read right away with a normal GET. Flexible Retrieval and Deep Archive objects must be restored before they can be read. A standard Deep Archive restore finishes within 12 hours.

The current names matter. Older material says just "S3 Glacier"; the class formerly called S3 Glacier is now S3 Glacier Flexible Retrieval. Reduced Redundancy Storage is deprecated, and AWS recommends Standard instead.

Minimum storage duration

Three numbers do most of the work on the exam: 30, 90 and 180 days. Standard-IA and One Zone-IA are 30. Glacier Instant Retrieval and Glacier Flexible Retrieval are 90. Glacier Deep Archive is 180. Standard and Intelligent-Tiering have no minimum.

The catch is early deletion. If you delete an object from a 30-day class after 10 days, you are still billed for the remainder of the 30 days. The Glacier classes also charge per-GB retrieval fees. This is why a question about data that will be kept only briefly should not point you to an archive class even though its storage price is low.

Lifecycle rules

S3 Lifecycle uses rules to transition objects to other storage classes or expire (delete) them. Those are the two action types. Rules apply to existing objects and to objects added later, and a bucket policy cannot block a Lifecycle rule from transitioning or deleting objects.

A classic path is Standard, then Standard-IA or Intelligent-Tiering, then Glacier Flexible Retrieval, then expiry. A typical scenario: a company keeps log files and wants them moved to a cheaper class after 90 days and deleted after seven years automatically. The answer is a Lifecycle rule. S3 Storage Class Analysis helps you decide when moving data from Standard to Standard-IA makes sense.

Features that get confused with classes

Versioning has a few traps. With versioning on, a delete adds a delete marker instead of removing the data. Once enabled, versioning can be suspended but never returned to unversioned. And you are billed for every stored version at normal rates. Live replication only copies new and updated objects; S3 Batch Replication copies objects that existed before.

Two security facts also appear: all new S3 objects have been encrypted automatically with SSE-S3 (AES-256) since January 5, 2023, at no extra cost, and the customer still decides on classification and permissions. That second point links back to the shared responsibility model.

Reading the question

Match the scenario to the keyword.

1. "Unknown or changing access pattern" points to Intelligent-Tiering.
2. "Cheaper, can be re-created, one AZ is fine" points to One Zone-IA.
3. "Archive, but must be readable immediately" points to Glacier Instant Retrieval.
4. "Lowest cost, accessed less than once a year" points to Deep Archive.
5. "Automatically move or delete after N days" points to Lifecycle.

Learning the table is a good place to use retrieval practice rather than rereading; how to memorize a list, a table or a formula sheet covers approaches that fit it. The Encodr course has a chapter on S3 and storage classes in its Storage Services unit as part of the AWS Cloud Practitioner flashcards. Cards test recall; they do not replace creating a bucket in the console and looking at the storage class options yourself. The course is unofficial and not affiliated with or endorsed by AWS.

For the surrounding plan, see what is on the exam and how to study for it. The practice questions include an S3 class item. For the Azure counterpart, Azure redundancy options explained covers how Microsoft handles the same durability-versus-cost trade-off.