DBS-C01 Workload-Specific Database Design Practice Question
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?
⚠ Common exam trap
It's easy for candidates to 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.
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
✓
Migrate to Amazon Aurora PostgreSQL and rewrite hierarchical queries to use recursive CTEs.
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.
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.
- ✗
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.
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