3.3 Determine high-performing database solutions.
Objective 3.3 sits in Design High-Performing Architectures, which carries 24% of the Solutions Architect Associate exam. The questions below are original, written from the official objective title above, and each explanation cites the AWS page it rests on.
Objective title verbatim from the official objectives. AWS exam page ↗
A worked example
Shown solved, with the whole explanation open: this is what every question here carries.
A payments service reads an item straight after a write that already returned HTTP 200, and it must never see the older value. Which read does that?
The concept
DynamoDB replicates an item across facilities before a read can be served from any of them. The read model decides whether the request waits for every copy to agree or answers from whichever copy responds first, and that choice costs latency and money in opposite directions.
Why this answer
Setting ConsistentRead to true makes DynamoDB return data that reflects every write that has already succeeded. A payment that has been acknowledged cannot be allowed to disappear on the next read, so the extra latency and the doubled read cost are worth paying.
- AThe default read may answer from a replica that has not caught up yet, which is why it costs half as much.
- Correct. ConsistentRead set to true reflects all prior successful writes.
- CEvery read from a global secondary index is eventually consistent, whatever the request asks for.
- DStream records arrive eventually consistent too, and a stream is a change feed rather than a way to read current state.
Now you: objective 3.3 questions
No account needed. The explanation opens when you answer.
Sample question 1 of 3
A query against a global secondary index sometimes misses an item written moments earlier, and the team needs that lookup strongly consistent. What changes?
Sample question 2 of 3
A leaderboard reads the same few DynamoDB items thousands of times a second, needs microsecond latency and minimal code change. What do you add?
Sample question 3 of 3
Analyst reports are slowing a Multi-AZ RDS instance that also serves production traffic. Where do you send the reporting queries?
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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.