- A
The application is using a read replica endpoint, which does not support write operations.
Why wrong: Read replicas are for read traffic only and are not used for failover.
- B
The application is using the RDS instance endpoint instead of the cluster endpoint, so it does not automatically route to the standby after failover.
The instance endpoint is static and remains pointed to the original primary; after failover, the application must reconnect to the new primary using the CNAME which takes time to update.
- C
The application is connecting through a Network Load Balancer, which is not configured for cross-zone failover.
Why wrong: Multi-AZ RDS does not use a load balancer; the failover is handled by DNS CNAME update.
- D
The application connection pool is exhausted because the failover caused all existing connections to drop simultaneously.
Why wrong: While connections drop, the outage is due to the endpoint not redirecting writes, not connection pool exhaustion.
DEA-C01 Data Store Management Practice Question
This DEA-C01 practice question tests your understanding of data store management. 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 is using Amazon RDS for MySQL with Multi-AZ deployment. They notice that during a recent failover test, the application experienced a brief write outage. The application uses a connection string that points to the RDS instance endpoint. What is the MOST likely cause of the write outage?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The application is using the RDS instance endpoint instead of the cluster endpoint, so it does not automatically route to the standby after failover.
Option B is correct because in a Multi-AZ RDS deployment, the instance endpoint always points to the current primary instance. During a failover, the DNS record for the instance endpoint is updated to point to the new primary, but existing connections to the old primary are dropped, and the DNS change can take time to propagate. The application's connection string using the instance endpoint means it does not automatically route to the standby during the failover transition, causing a brief write outage until the DNS update completes and the application reconnects. In contrast, using a cluster endpoint (available for Aurora, not standard RDS) or implementing retry logic in the application would mitigate this.
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.
- ✗
The application is using a read replica endpoint, which does not support write operations.
Why it's wrong here
Read replicas are for read traffic only and are not used for failover.
- ✓
The application is using the RDS instance endpoint instead of the cluster endpoint, so it does not automatically route to the standby after failover.
Why this is correct
The instance endpoint is static and remains pointed to the original primary; after failover, the application must reconnect to the new primary using the CNAME which takes time to update.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The application is connecting through a Network Load Balancer, which is not configured for cross-zone failover.
Why it's wrong here
Multi-AZ RDS does not use a load balancer; the failover is handled by DNS CNAME update.
- ✗
The application connection pool is exhausted because the failover caused all existing connections to drop simultaneously.
Why it's wrong here
While connections drop, the outage is due to the endpoint not redirecting writes, not connection pool exhaustion.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the RDS instance endpoint with the cluster endpoint used in Amazon Aurora, assuming that Multi-AZ automatically provides a seamless, zero-downtime failover for writes, when in fact the instance endpoint requires DNS propagation and connection re-establishment.
Detailed technical explanation
How to think about this question
Under the hood, RDS Multi-AZ uses synchronous replication to a standby in a different Availability Zone, and failover is triggered by a DNS CNAME update that points the instance endpoint to the new primary's private IP. The Time-To-Live (TTL) for this DNS record is typically 30 seconds, meaning clients caching the old DNS entry may experience write failures for up to that duration. In real-world scenarios, applications should implement retry logic with exponential backoff and use a connection pool that validates connections before use to handle the brief outage gracefully.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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.
- →
Data Store Management — study guide chapter
Learn the concepts, then practise the questions
- →
Data Store Management practice questions
Targeted practice on this topic area only
- →
All DEA-C01 questions
1,786 questions across all exam domains
- →
AWS Certified Data Engineer Associate DEA-C01 study guide
Full concept coverage aligned to exam objectives
- →
DEA-C01 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related DEA-C01 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Data Ingestion and Transformation practice questions
Practise DEA-C01 questions linked to Data Ingestion and Transformation.
Data Operations and Support practice questions
Practise DEA-C01 questions linked to Data Operations and Support.
Data Security and Governance practice questions
Practise DEA-C01 questions linked to Data Security and Governance.
Data Store Management practice questions
Practise DEA-C01 questions linked to Data Store Management.
DEA-C01 fundamentals practice questions
Practise DEA-C01 questions linked to DEA-C01 fundamentals.
DEA-C01 scenario practice questions
Practise DEA-C01 questions linked to DEA-C01 scenario.
DEA-C01 troubleshooting practice questions
Practise DEA-C01 questions linked to DEA-C01 troubleshooting.
Practice this exam
Start a free DEA-C01 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this DEA-C01 question test?
Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The application is using the RDS instance endpoint instead of the cluster endpoint, so it does not automatically route to the standby after failover. — Option B is correct because in a Multi-AZ RDS deployment, the instance endpoint always points to the current primary instance. During a failover, the DNS record for the instance endpoint is updated to point to the new primary, but existing connections to the old primary are dropped, and the DNS change can take time to propagate. The application's connection string using the instance endpoint means it does not automatically route to the standby during the failover transition, causing a brief write outage until the DNS update completes and the application reconnects. In contrast, using a cluster endpoint (available for Aurora, not standard RDS) or implementing retry logic in the application would mitigate this.
What should I do if I get this DEA-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 24, 2026
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.