Objective 4.3SAA-C03

4.3 Design cost-optimized database solutions.

Objective 4.3 sits in Design Cost-Optimized Architectures, which carries 20% of the Solutions Architect Associate exam. The questions below are original, written from the official objective title above, and each explanation cites the Amazon Web Services (AWS) page it rests on.

Objective title verbatim from the official objectives. Amazon Web Services (AWS) exam page

A worked example

Shown solved, with the whole explanation open: this is what every question here carries.

4-3Design Cost-Optimized ArchitecturesModerate

A DynamoDB table's traffic has been flat for two years and the team can forecast next quarter's request rate closely. Which capacity choice costs least here?

On-demand, with pay-per-request pricingPay-per-request suits workloads nobody can size. It carries a premium that a forecastable table does not need to pay.
Provisioned, set from the forecast rateCorrect · your answerCorrect. A reliable forecast makes a declared rate the cheaper trade.
On-demand with a maximum request rateA maximum request rate is not part of on-demand mode. Throughput management is what the mode hands to DynamoDB.
Standard-IA table class with on-demandTable class governs the balance between storage and throughput pricing, which is a separate axis from capacity mode.

Correct.

Concept

Paying per request removes the risk of guessing wrong, and that insurance is priced into the unit rate. Where demand is genuinely predictable there is no risk left to insure, so committing to a rate is the cheaper trade.

Why B

Provisioned mode bills for the hourly capacity you declare rather than what you consume, which AWS recommends for steady workloads with predictable growth that can be forecast reliably. That description matches this table exactly.

Source

#dynamodb#capacity-mode#cost-optimization

Now you: objective 4.3 questions

No account needed. The explanation opens when you answer.

Sample question 1 of 3

4-3Design Cost-Optimized ArchitecturesModerate

A table holds years of order history queried a few times a month, and storage is far and away the largest line on its bill. What do you change?

Sample question 2 of 3

4-3Design Cost-Optimized ArchitecturesHard

A team stops a development RDS instance each Friday and starts it again on Monday, then finds the saving smaller than expected. What are they still paying for?

Sample question 3 of 3

4-3Design Cost-Optimized ArchitecturesModerate

A team holds a reserved db.r5.large for RDS for PostgreSQL and scales the running instance up to db.r5.xlarge. What happens to that reservation?

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Read the sources

These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.

More objectives in Design Cost-Optimized Architectures