The correct approach is to migrate to Amazon RDS for PostgreSQL and implement the extension’s functionality using AWS Lambda functions called via triggers. This design is correct because RDS for PostgreSQL does not support custom extensions, but it does support native triggers that can invoke Lambda functions through the aws_lambda extension. By offloading the advanced statistical analysis to Lambda, the company preserves the existing database schema and query patterns, minimizing application changes while handling unsupported logic externally. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of RDS limitations versus Aurora or self-managed options, and the common trap is to suggest migrating to Aurora or EC2, which would require more rework. Remember the memory tip: “Trigger Lambda, not custom code” — when an extension is blocked, push the compute to Lambda via a database trigger.
DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. 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. 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 migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database currently uses a custom extension that is not supported by RDS. The application relies heavily on this extension for advanced statistical analysis. Which design approach should the company take to minimize application changes?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Migrate to Amazon RDS for PostgreSQL and implement the extension's functionality using AWS Lambda functions called via triggers.
Option D is correct because it allows the company to offload the unsupported custom extension's statistical analysis logic to AWS Lambda functions, which can be invoked via RDS PostgreSQL triggers. This approach minimizes application changes by keeping the database schema and query patterns largely intact, while the Lambda functions handle the advanced computations externally. RDS does not allow custom extensions, so this pattern leverages RDS for PostgreSQL's native trigger support to integrate with Lambda without modifying the application's core database interactions.
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.
✗
Migrate to PostgreSQL on Amazon EC2 and install the custom extension.
Why it's wrong here
EC2 adds operational overhead and is not the minimal change approach.
✗
Migrate to Amazon DynamoDB and implement statistical analysis using DynamoDB streams and Lambda.
Why it's wrong here
DynamoDB is not relational and would require significant application changes.
✗
Migrate to Amazon RDS for PostgreSQL and install the custom extension on the RDS instance.
Why it's wrong here
RDS for PostgreSQL does not support custom extensions.
✓
Migrate to Amazon RDS for PostgreSQL and implement the extension's functionality using AWS Lambda functions called via triggers.
Why this is correct
Lambda can replicate the extension's behavior without modifying the application.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
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 assume RDS for PostgreSQL supports all PostgreSQL extensions, but AWS explicitly restricts custom extensions, making Option C a common distractor that seems plausible but is technically impossible.
Detailed technical explanation
How to think about this question
Under the hood, the aws_lambda extension in RDS for PostgreSQL enables triggers to invoke Lambda functions synchronously or asynchronously, passing row-level data as JSON. This pattern is ideal for offloading CPU-intensive or unsupported operations like custom statistical functions, but it introduces latency and potential cold starts; for real-time analytics, consider using Lambda provisioned concurrency. A subtle behavior is that the trigger must be defined on the table, and the Lambda function must handle idempotency if the trigger fires multiple times due to retries.
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.
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: Migrate to Amazon RDS for PostgreSQL and implement the extension's functionality using AWS Lambda functions called via triggers. — Option D is correct because it allows the company to offload the unsupported custom extension's statistical analysis logic to AWS Lambda functions, which can be invoked via RDS PostgreSQL triggers. This approach minimizes application changes by keeping the database schema and query patterns largely intact, while the Lambda functions handle the advanced computations externally. RDS does not allow custom extensions, so this pattern leverages RDS for PostgreSQL's native trigger support to integrate with Lambda without modifying the application's core database interactions.
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.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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