- A
Deploy with one or more read replicas in the same region
Why wrong: Read replicas use asynchronous replication, which can introduce read-after-write inconsistency. They are not suitable when strong consistency is required.
- B
Deploy with cross-region replicas
Why wrong: Cross-region replicas have higher latency and also use asynchronous replication, so they do not guarantee read-after-write consistency.
- C
Deploy as a single-AZ instance with increased instance size
A single-AZ instance with increased size provides consistent reads from the primary and low latency, meeting both requirements without replication overhead.
- D
Deploy as Multi-AZ with a synchronous standby
Why wrong: Multi-AZ provides synchronous replication for high availability, but the standby is not used for reads and synchronous replication adds write latency, which may not be necessary for the given requirements.
DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 is deploying a new Amazon RDS for PostgreSQL database. The database will be used by an application that requires read-after-write consistency and low latency. Which deployment configuration is MOST suitable?
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
Deploy as a single-AZ instance with increased instance size
Read replicas in RDS for PostgreSQL use asynchronous replication and do not guarantee read-after-write consistency. For an application requiring read-after-write consistency and low latency, the best choice is to deploy as a single-AZ instance with increased instance size. This avoids replication lag entirely, ensuring that reads from the primary instance always reflect the latest writes, while scaling up provides low latency for both reads and writes.
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.
- ✗
Deploy with one or more read replicas in the same region
Why it's wrong here
Read replicas use asynchronous replication, which can introduce read-after-write inconsistency. They are not suitable when strong consistency is required.
- ✗
Deploy with cross-region replicas
Why it's wrong here
Cross-region replicas have higher latency and also use asynchronous replication, so they do not guarantee read-after-write consistency.
- ✓
Deploy as a single-AZ instance with increased instance size
Why this is correct
A single-AZ instance with increased size provides consistent reads from the primary and low latency, meeting both requirements without replication overhead.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Deploy as Multi-AZ with a synchronous standby
Why it's wrong here
Multi-AZ provides synchronous replication for high availability, but the standby is not used for reads and synchronous replication adds write latency, which may not be necessary for the given requirements.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing Multi-AZ synchronous standby with read replicas, assuming that a standby replica can serve read traffic, when in fact it is only used for automatic failover and does not offload read queries.
Detailed technical explanation
How to think about this question
Amazon RDS read replicas use PostgreSQL's native streaming replication, which is asynchronous by default but within the same region the replication lag is typically sub-second, enabling near real-time read-after-write consistency. The application can use the reader endpoint to distribute read traffic across replicas, while writes still go to the primary instance, ensuring low latency for both operations. In contrast, Multi-AZ uses synchronous replication to a standby in a different Availability Zone, but that standby cannot serve reads, making it unsuitable for read scaling.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Deployment and Migration — This question tests Deployment and Migration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deploy as a single-AZ instance with increased instance size — Read replicas in RDS for PostgreSQL use asynchronous replication and do not guarantee read-after-write consistency. For an application requiring read-after-write consistency and low latency, the best choice is to deploy as a single-AZ instance with increased instance size. This avoids replication lag entirely, ensuring that reads from the primary instance always reflect the latest writes, while scaling up provides low latency for both reads and writes.
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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