SAP-C03 practice question: Database capacity modes and reserved capacity
Cost-Optimized Architecture Design A free question from our original SAP-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.
A retailer runs an Amazon Aurora PostgreSQL cluster for its orders. The writer instance and two readers run around the clock, and the team expects that load to continue for at least three years.
A separate Amazon DynamoDB table holds shopping carts, and its traffic is very uneven, with sharp spikes during sales. The development and test databases are needed only during working hours.
Which TWO changes will reduce cost without reducing the capacity available to production? (Choose two.)
Choose two answers.
AA. Move the always-on Aurora writer and readers to Aurora Serverless v2, so that capacity is billed by the second as load changes.
BB. Buy reserved capacity for the Aurora writer and readers for three years, so their steady-state instance hours are billed at the committed rate.
CC. Set the cart table to on-demand capacity mode, so each spike is billed for the requests it actually uses without capacity planning.
DD. Set the cart table to provisioned capacity at the highest level seen during the last sale, so no spike is ever throttled.
EE. Keep the development databases running around the clock on their current instances, so that developers never wait for a database to start each morning.
Show the answer and explanation
Answers: B, C
A. Wrong: The cluster's load is steady, so the per-second billing of Serverless v2 would be paid around the clock at a higher effective rate than a commitment. This option raises cost for this pattern.
B. Right: Correct. Reserved capacity for a steady, three-year workload gives a lower committed rate on the instance hours, and the cluster keeps its current size. The commitment matches the expected load.
C. Right: Correct. On-demand capacity mode bills per request and absorbs uneven spikes without provisioning, which suits a cart table with sharp sales peaks. The table keeps its full capacity during spikes.
D. Wrong: A fixed level sized for the peak pays for that capacity all year, which wastes money in quiet periods. The option raises cost on a table with uneven traffic.
E. Wrong: Running non-production databases all day and night multiplies their instance cost for no benefit. Stopping them outside working hours is the cheaper approach.
Explanation
Reserved capacity fits the three-year steady Aurora load, and on-demand capacity mode fits the spiky cart table without over-provisioning. Serverless v2 costs more for steady load, while fixed peak capacity and always-on test databases waste money.
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