The answer is to increase the RDS instance size to a larger instance class. This directly addresses MySQL replication lag during migration because the target RDS instance is the bottleneck when applying writes from a write-heavy source; a larger instance provides more CPU and memory resources to process the binary log events faster, reducing the Seconds_Behind_Master value. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding that replication lag is typically a target-side issue, not a source or network problem—a common trap is to suggest Multi-AZ or DMS, but Multi-AZ only enhances availability, not apply speed, and DMS is unnecessary when native replication is already configured. Remember the memory tip: when lag grows, the target is slow—scale up the RDS class to make the lag pass.
DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. 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 has a 100 GB MySQL database on an EC2 instance. They want to migrate to Amazon RDS for MySQL with minimal downtime. They have set up replication from the source to the target using MySQL native replication. After enabling replication, the 'Seconds_Behind_Master' value is increasing. The source database is write-heavy. What should the team do to reduce replication lag?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the RDS instance size to a larger instance class.
Option B is correct: using a larger RDS instance class provides more resources to apply changes. Option A is wrong because enabling Multi-AZ does not improve replication performance. Option C is wrong because DMS is not needed. Option D is wrong because tuning the source may help but the target is the bottleneck.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Tune the source database to reduce write load.
Why it's wrong here
May not be possible or sufficient; target is the bottleneck.
✗
Enable Multi-AZ on the RDS instance.
Why it's wrong here
Multi-AZ is for high availability, not performance.
✓
Increase the RDS instance size to a larger instance class.
Static NAT maps one inside address to one outside address.
✗
Switch to AWS DMS for migration.
Why it's wrong here
Replication lag is not a DMS issue if native replication is used.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. 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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DBS-C01 NAT questions on configuration and troubleshooting.
Deployment and Migration — This question tests Deployment and Migration — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Increase the RDS instance size to a larger instance class. — Option B is correct: using a larger RDS instance class provides more resources to apply changes. Option A is wrong because enabling Multi-AZ does not improve replication performance. Option C is wrong because DMS is not needed. Option D is wrong because tuning the source may help but the target is the bottleneck.
What should I do if I get this DBS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DBS-C01 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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