SAA-C03 domain - 20% of the exam

Design Cost-Optimized Architectures

Design Cost-Optimized Architectures is 20% of the AWS Certified Solutions Architect - Associate (SAA-C03) exam. These are the objectives it covers, each with practice questions and worked explanations.

Objectives in this domain

Sample question from this domain

Free sampleDesign Cost-Optimized Architecturesmedium

A SaaS company stores user-uploaded documents in Amazon S3. Some objects are downloaded many times in the first week, others are never touched again, and the access pattern for any given object is impossible to predict. The team wants to minimise storage cost without writing code to track access, and it cannot accept per-object retrieval fees or any change to how the application reads objects. Which storage approach meets these requirements?

  • AKeep every object in S3 Standard and rely on volume discounts to reduce the monthly storage charge as the bucket grows over time.
  • BPlace all objects in S3 Standard-Infrequent Access on upload, accepting the lower storage rate in exchange for the per-gigabyte retrieval charge on each read.
  • CWrite a lifecycle rule that moves every object to S3 Glacier Flexible Retrieval seven days after upload to capture the lowest possible storage price.
  • DStore all objects in S3 Intelligent-Tiering so the service automatically moves each object between access tiers based on its observed usage. Correct
Choose S3 Intelligent-Tiering when per-object access is unpredictable and you need automatic cost optimisation without retrieval fees or application changes. S3 Intelligent-Tiering automatically moves each object between a frequent-access tier and an infrequent-access tier based on its own monitored access, charging only a small monitoring fee and no retrieval fee. Because the tiering is per object and transparent to readers, it handles an unpredictable mix of hot and cold objects without code or retrieval penalties, which a single fixed storage class cannot do.

Why A is wrong: Tempting because S3 Standard needs no changes and avoids retrieval fees, but it applies the full frequent-access price to cold objects, so it does not minimise cost for data that is rarely read.

Why B is wrong: Tempting because Standard-IA is cheaper to store, but objects read many times in the first week incur per-gigabyte retrieval fees, which the requirement explicitly forbids.

Why C is wrong: Tempting because Glacier storage is cheap, but objects still read after seven days would need a retrieval job and wait, breaking the no-retrieval-fee and no-application-change constraints.

Why D is correct: Intelligent-Tiering monitors each object and shifts it between frequent and infrequent tiers automatically with no retrieval fees and no application change, which fits an unpredictable per-object access pattern.

Other domains in this exam

See also the SAA-C03 cert hub, the study guide, and the cheat sheet.

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