The answer is to migrate to Aurora PostgreSQL and rewrite the hierarchical queries using recursive CTEs. This is correct because Aurora PostgreSQL supports the WITH RECURSIVE clause, which directly maps to Oracle’s CONNECT BY logic, allowing you to preserve the parent-child traversal structure with only a syntax rewrite rather than a full application redesign. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of Aurora engine capabilities and the trade-offs between licensing cost reduction and application changes—a common trap is assuming Aurora MySQL can handle hierarchical queries, but it lacks both CONNECT BY and recursive CTE support. Remember that PostgreSQL is the only Aurora engine that can natively emulate Oracle’s hierarchical patterns, making it the least disruptive path. Memory tip: “PostgreSQL Recursive CTE replaces Oracle CONNECT BY—think PRC for PostgreSQL Recursive Connect.”
DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. 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 uses Amazon RDS for Oracle with a custom application that generates complex hierarchical queries using CONNECT BY. They want to migrate to Amazon Aurora to reduce licensing costs. Which migration strategy requires the fewest application changes?
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 Aurora PostgreSQL and rewrite hierarchical queries to use recursive CTEs.
Option C is correct because Aurora PostgreSQL supports recursive Common Table Expressions (CTEs) via the WITH RECURSIVE clause, which can be used to rewrite Oracle's CONNECT BY hierarchical queries with minimal application changes. This approach avoids the licensing costs of Oracle while preserving the hierarchical query logic, requiring only a syntax rewrite rather than a complete redesign. Aurora MySQL does not support CONNECT BY or recursive CTEs, making PostgreSQL the only Aurora engine that can handle this workload without significant application restructuring.
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.
✗
Use AWS Database Migration Service (DMS) to migrate directly to Aurora with no application changes.
Why it's wrong here
DMS migrates data, but queries still need to be rewritten.
✗
Migrate to Amazon Aurora MySQL and use its hierarchical query features.
Why it's wrong here
Aurora MySQL does not support recursive CTEs or CONNECT BY.
✓
Migrate to Amazon Aurora PostgreSQL and rewrite hierarchical queries to use recursive CTEs.
Why this is correct
PostgreSQL supports recursive CTEs, which are equivalent to CONNECT BY.
Related concept
Read the scenario before looking for a memorised answer.
✗
Migrate to Amazon RDS for SQL Server and use its recursive CTEs.
Why it's wrong here
SQL Server is also licensed, not reducing costs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume Aurora MySQL can handle hierarchical queries because it is often marketed as Oracle-compatible, but it lacks CONNECT BY and recursive CTEs, making PostgreSQL the only Aurora engine that can natively support hierarchical queries with a straightforward rewrite.
Detailed technical explanation
How to think about this question
Oracle's CONNECT BY is a proprietary hierarchical query clause that uses PRIOR to define parent-child relationships, while PostgreSQL's recursive CTEs use the WITH RECURSIVE syntax with a UNION ALL to iterate through levels. Under the hood, both engines execute similar tree-traversal algorithms, but PostgreSQL's CTE approach is SQL-standard (ISO/IEC 9075:2016) and more portable. In a real-world migration, you must also handle Oracle-specific features like NOCYCLE, CONNECT_BY_ISCYCLE, and SYS_CONNECT_BY_PATH, which require careful translation to PostgreSQL's cycle detection and path aggregation using array_append or string_agg.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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 Aurora PostgreSQL and rewrite hierarchical queries to use recursive CTEs. — Option C is correct because Aurora PostgreSQL supports recursive Common Table Expressions (CTEs) via the WITH RECURSIVE clause, which can be used to rewrite Oracle's CONNECT BY hierarchical queries with minimal application changes. This approach avoids the licensing costs of Oracle while preserving the hierarchical query logic, requiring only a syntax rewrite rather than a complete redesign. Aurora MySQL does not support CONNECT BY or recursive CTEs, making PostgreSQL the only Aurora engine that can handle this workload without significant application restructuring.
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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Question Discussion
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