- A
Modify the source DB instance to use a larger instance class.
Why wrong: Modifying the source to a larger instance class may help with resource constraints, but the core issue is that cross-region replication without Multi-AZ puts excessive load on the primary. Multi-AZ is the direct and required fix.
- B
Delete the replica and create a new one from a snapshot.
Why wrong: Deleting and recreating from a snapshot does not address the underlying cause of lag; the new replica would likely experience the same issue if Multi-AZ is not enabled.
- C
Increase the backup retention period to 35 days.
Why wrong: Increasing the backup retention period has no effect on replication lag. Backup retention is for point-in-time recovery, not replication performance.
- D
Enable Multi-AZ on the source database instance.
Enabling Multi-AZ on the source DB instance is the correct solution because cross-region read replicas in RDS PostgreSQL require Multi-AZ to replicate from the standby, reducing load on the primary and thus decreasing replication lag.
Reducing Cross-Region Read Replica Lag in RDS PostgreSQL — AWS Data Engineer Associate
This DEA-C01 practice question tests your understanding of data store management. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: cross-region read replica. 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 data engineering team is responsible for an Amazon RDS for PostgreSQL instance that stores financial data. The database is 500 GB in size. The team needs to create a read replica in a different AWS Region for disaster recovery. The source database has automated backups enabled with a retention period of 7 days. The team initiates the cross-region read replica creation. After several hours, the replica status shows 'Replication Lag' of 30 minutes and is increasing. What should the team do to reduce the replication lag?
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 Multi-AZ on the source database instance.
Enabling Multi-AZ on the source RDS for PostgreSQL instance adds a synchronous standby in a different Availability Zone. This reduces the I/O load on the primary because the synchronous standby can offload some of the write-ahead log (WAL) generation and replication tasks. With less resource contention on the primary, the cross-region read replica can receive WAL data more quickly, thereby reducing replication lag.
Key principle: Cross-region read replica
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Modify the source DB instance to use a larger instance class.
Why it's wrong here
Modifying the source to a larger instance class may help with resource constraints, but the core issue is that cross-region replication without Multi-AZ puts excessive load on the primary. Multi-AZ is the direct and required fix.
- ✗
Delete the replica and create a new one from a snapshot.
Why it's wrong here
Deleting and recreating from a snapshot does not address the underlying cause of lag; the new replica would likely experience the same issue if Multi-AZ is not enabled.
- ✗
Increase the backup retention period to 35 days.
Why it's wrong here
Increasing the backup retention period has no effect on replication lag. Backup retention is for point-in-time recovery, not replication performance.
- ✓
Enable Multi-AZ on the source database instance.
Why this is correct
Enabling Multi-AZ on the source DB instance is the correct solution because cross-region read replicas in RDS PostgreSQL require Multi-AZ to replicate from the standby, reducing load on the primary and thus decreasing replication lag.
Related concept
Cross-region read replica
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often think that increasing the source instance size (Option A) will reduce replication lag because a larger instance can handle more load. However, cross-region replication lag is primarily caused by the overhead of generating and shipping WAL data over a network. Enabling Multi-AZ on the source database offloads synchronous writes to a standby instance, reducing the I/O load on the primary and allowing it to dedicate more resources to WAL generation and shipping, thereby reducing lag.
Detailed technical explanation
How to think about this question
Cross-region read replicas in RDS for PostgreSQL use PostgreSQL's streaming replication protocol to ship WAL segments from the source to the replica. When the source is a Single-AZ instance, it must handle both application writes and WAL shipping, which can cause contention. Enabling Multi-AZ creates a synchronous standby in the same region that can take over WAL shipping duties, effectively reducing the load on the primary and allowing the cross-region replica to receive WAL data with lower latency. In practice, this can reduce replication lag from minutes to seconds under heavy write loads.
KKey Concepts to Remember
- Cross-region read replica
- Multi-AZ deployment
- Replication lag
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
Cross-region read replica
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Review cross-region read replica, then practise related DEA-C01 questions on the same topic to reinforce the concept.
- →
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 — Cross-region read replica.
What is the correct answer to this question?
The correct answer is: Enable Multi-AZ on the source database instance. — Enabling Multi-AZ on the source RDS for PostgreSQL instance adds a synchronous standby in a different Availability Zone. This reduces the I/O load on the primary because the synchronous standby can offload some of the write-ahead log (WAL) generation and replication tasks. With less resource contention on the primary, the cross-region read replica can receive WAL data more quickly, thereby reducing replication lag.
What should I do if I get this DEA-C01 question wrong?
Review cross-region read replica, then practise related DEA-C01 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Cross-region read replica
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 →
Keep practising
More DEA-C01 practice questions
- A data pipeline uses Kinesis Data Firehose to deliver streaming data to an S3 bucket. The data volume spikes occasionall…
- An e-commerce company uses AWS Glue to run ETL jobs that transform clickstream data from Amazon S3. The job reads Parque…
- A data engineering team uses Amazon Kinesis Data Analytics for Apache Flink to process streaming data. They notice that…
- A company uses AWS Glue to process streaming data from Amazon Kinesis Data Streams. The job reads JSON records and write…
- A data engineer applies the above bucket policy to an S3 bucket containing sensitive data. The goal is to allow only enc…
- A company uses AWS Glue to catalog data in Amazon S3. The security team requires that all sensitive data be identified a…
Last reviewed: Jul 4, 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.