DBS-C01 Workload-Specific Database Design Practice Question
Which THREE factors should be considered when choosing between Amazon RDS and Amazon DynamoDB for a new application? (Choose 3.)
⚠ Common exam trap
It's easy for candidates to assume encryption at rest is exclusive to one service, but both RDS and DynamoDB support it via AWS KMS, making it a non-differentiating factor.
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
✓
Access patterns (predictable vs. ad-hoc)
Amazon RDS is a relational database service that excels at complex queries involving joins and aggregations, while DynamoDB is a NoSQL key-value and document database optimized for predictable, high-scale access patterns. The choice between them hinges on whether the application requires relational features (RDS) or can tolerate denormalized schemas for low-latency, horizontal scaling (DynamoDB). Option C is correct because DynamoDB is designed for ad-hoc, single-key lookups and simple queries, whereas RDS supports complex, ad-hoc SQL queries with joins.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Cost of storage
Why it's wrong here
Both have cost-effective options.
- ✗
Need for encryption at rest
Why it's wrong here
Both support encryption at rest.
- ✓
Access patterns (predictable vs. ad-hoc)
Why this is correct
DynamoDB suits predictable patterns; RDS for complex queries.
- ✓
Scalability requirements (horizontal vs. vertical)
Why this is correct
DynamoDB scales horizontally; RDS scales vertically.
- ✓
Query complexity (joins, aggregations)
Why this is correct
RDS supports complex queries; DynamoDB is simple key-value.
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