- A
Enable binary log replication with parallel apply on replicas.
Correct. Enabling binary log parallel apply on replicas allows multiple transactions to be applied concurrently, reducing the time for the replica to catch up to the writer.
- B
Use a lower transaction isolation level (e.g., READ COMMITTED) on replicas.
Correct. Using READ COMMITTED isolation on replicas reduces locking overhead, which speeds up the apply process and decreases replication lag.
- C
Implement synchronous replication between writer and replicas.
Why wrong: Incorrect. Synchronous replication is not supported in Amazon Aurora; Aurora uses asynchronous replication, so this strategy is not available.
- D
Use Aurora Auto Scaling to add read replicas during peak traffic.
Why wrong: Incorrect. Adding read replicas does not reduce replication lag; it can increase the replication load and potentially worsen lag because the writer must send changes to more replicas.
- E
Increase the instance size of the writer instance.
Correct. Increasing the instance size of the writer instance can help if the writer is a bottleneck, allowing it to generate binlog entries faster and thereby reducing replication lag.
DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company runs an e-commerce platform on Amazon Aurora MySQL. The platform experiences high traffic during flash sales. To handle the load, they want to offload read traffic to read replicas. However, they are concerned about replication lag causing stale data for inventory checks. Which three strategies can reduce replication lag? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Enable binary log replication with parallel apply on replicas.
Options A, B, and E are effective strategies to reduce replication lag in Amazon Aurora MySQL. Enabling binary log parallel apply on replicas (A) allows concurrent application of transactions, reducing lag. Using a lower isolation level like READ COMMITTED (B) reduces locking contention on replicas, improving apply performance. Increasing the writer instance size (E) helps if the writer is resource-constrained, allowing faster binlog generation and reducing replication delay. Option D (adding read replicas) does not reduce replication lag; in fact, adding more replicas can increase the replication load and potentially increase lag. Option C (synchronous replication) is not available in Aurora; replication is asynchronous.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Enable binary log replication with parallel apply on replicas.
Why this is correct
Correct. Enabling binary log parallel apply on replicas allows multiple transactions to be applied concurrently, reducing the time for the replica to catch up to the writer.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Use a lower transaction isolation level (e.g., READ COMMITTED) on replicas.
Why this is correct
Correct. Using READ COMMITTED isolation on replicas reduces locking overhead, which speeds up the apply process and decreases replication lag.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Implement synchronous replication between writer and replicas.
Why it's wrong here
Incorrect. Synchronous replication is not supported in Amazon Aurora; Aurora uses asynchronous replication, so this strategy is not available.
- ✗
Use Aurora Auto Scaling to add read replicas during peak traffic.
Why it's wrong here
Incorrect. Adding read replicas does not reduce replication lag; it can increase the replication load and potentially worsen lag because the writer must send changes to more replicas.
- ✓
Increase the instance size of the writer instance.
Why this is correct
Correct. Increasing the instance size of the writer instance can help if the writer is a bottleneck, allowing it to generate binlog entries faster and thereby reducing replication lag.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse synchronous replication (which is not available in Aurora) with the Multi-AZ failover feature, or incorrectly assume that scaling the writer instance size will directly reduce replication lag, when in fact lag is primarily a replica-side issue.
Detailed technical explanation
How to think about this question
Aurora MySQL read replicas use asynchronous replication based on the cluster volume, where the writer writes to a shared distributed storage layer and replicas read from it. Parallel apply in binary log replication works by grouping transactions that are independent (no conflicting row locks) and applying them simultaneously, which is particularly effective when the replica has multiple CPU cores. In practice, during flash sales, enabling parallel apply can reduce lag from seconds to milliseconds by leveraging the replica's multi-threaded apply capability.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable binary log replication with parallel apply on replicas. — Options A, B, and E are effective strategies to reduce replication lag in Amazon Aurora MySQL. Enabling binary log parallel apply on replicas (A) allows concurrent application of transactions, reducing lag. Using a lower isolation level like READ COMMITTED (B) reduces locking contention on replicas, improving apply performance. Increasing the writer instance size (E) helps if the writer is resource-constrained, allowing faster binlog generation and reducing replication delay. Option D (adding read replicas) does not reduce replication lag; in fact, adding more replicas can increase the replication load and potentially increase lag. Option C (synchronous replication) is not available in Aurora; replication is asynchronous.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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