DBS-C01 Sharding (Application-Level) Practice Question
A company is designing a document database on Amazon DocumentDB for a content management system. Which TWO design practices improve query performance and reduce costs?
⚠ Common exam trap
Candidates often think DocumentDB supports native sharding like MongoDB. In reality, Amazon DocumentDB does not support sharding. Proper indexing is the primary performance optimization for DocumentDB.
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
✓
Use appropriate indexes to support common query patterns.
In Amazon DocumentDB, only Option E (Use appropriate indexes to support common query patterns) is correct. Sharding (Option A) is not supported by DocumentDB. Options B, C, and D are incorrect because they would degrade performance or increase costs. Note: The question asks for two, but only one option is correct.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Shard data based on access patterns to distribute load.
Why it's wrong here
Correct: Sharding data based on access patterns distributes load across instances, improving throughput and reducing latency, even if implemented at the application level.
- ✗
Design documents to avoid joins by frequently using $lookup.
Why it's wrong here
Incorrect: Frequently using $lookup performs joins, which are expensive in document databases. Denormalization is preferred to avoid joins.
- ✗
Avoid denormalization to maintain strict normal forms.
Why it's wrong here
Avoiding denormalization is contrary to document database best practices. Denormalizing related data into a single document avoids expensive joins and improves read performance, which reduces costs and latency. Therefore, this option is incorrect.
- ✗
Store all documents in a single collection without indexes to reduce overhead.
Why it's wrong here
Incorrect: Storing documents without indexes forces full collection scans, severely degrading query performance and increasing costs.
- ✓
Use appropriate indexes to support common query patterns.
Why this is correct
Correct: Using appropriate indexes minimizes the amount of data scanned, speeding up queries and reducing I/O costs.
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