DBS-C01 Deployment and Migration Practice Question
A company is deploying a MongoDB-compatible database using Amazon DocumentDB. The application requires the ability to perform ad-hoc queries on nested fields within documents. Which DocumentDB feature should be enabled to meet this requirement?
⚠ Common exam trap
Many exam-takers confuse indexing features with operational features like TTL or Change streams, assuming any advanced DocumentDB feature can support nested queries, when only explicit indexing on nested fields enables efficient ad-hoc querying on sub-documents.
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
✓
Indexes on nested fields
Amazon DocumentDB supports indexing on nested fields, which allows efficient querying of sub-documents and arrays within documents. By creating indexes on specific nested paths (e.g., "address.city"), the query engine can perform index scans instead of full collection scans, enabling fast ad-hoc queries on nested fields. This feature directly meets the requirement for ad-hoc queries on nested fields.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
TTL indexes
Why it's wrong here
TTL indexes automatically delete documents after a period.
- ✓
Indexes on nested fields
Why this is correct
Indexes allow efficient ad-hoc queries on nested fields.
- ✗
Transactions
Why it's wrong here
Transactions provide ACID guarantees, not query optimization.
- ✗
Change streams
Why it's wrong here
Change streams capture changes, not query optimization.
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