The answer is to convert secondary indexes to the DocumentDB-compatible format. This is the most important design consideration because Amazon DocumentDB uses a different indexing engine than MongoDB; while it supports secondary indexes, it does not support all MongoDB index types—such as sparse, partial, or TTL indexes—and failing to convert them can lead to degraded query performance or index creation failures. On the AWS Certified Database Specialty DBS-C01 exam, this question tests your understanding of migration compatibility and the need to refactor database schemas for the target service, often appearing as a trap where candidates assume full MongoDB API parity. A common mistake is to focus on scaling or caching solutions, but the core requirement for low-latency reads hinges on properly converted indexes. Memory tip: “Indexes are not plug-and-play—convert before you migrate.”
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 is migrating an on-premises MongoDB database to Amazon DocumentDB. The application uses secondary indexes extensively and requires low-latency reads. Which database design consideration is MOST important for this workload?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Convert secondary indexes to the DocumentDB-compatible format
Option B is correct because Amazon DocumentDB does not support the same range of secondary indexes as MongoDB; converting indexes ensures performance. Option A is wrong because DocumentDB uses its own storage, not EBS. Option C is wrong because DynamoDB Accelerator is for DynamoDB, not DocumentDB. Option D is wrong because vertical scaling is often insufficient; proper indexing is key.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Convert secondary indexes to the DocumentDB-compatible format
Why this is correct
DocumentDB requires indexes to be created in its own format; otherwise queries may not use them.
Related concept
Static NAT maps one inside address to one outside address.
✗
Provision EBS-optimized instances with increased IOPS
Why it's wrong here
DocumentDB uses Amazon EBS volumes, but performance tuning should focus on indexes.
✗
Use a larger instance type to avoid indexing issues
Why it's wrong here
Vertical scaling does not solve indexing compatibility problems.
✗
Enable DynamoDB Accelerator (DAX) for caching
Why it's wrong here
DAX is for DynamoDB, not DocumentDB.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DBS-C01 NAT questions on configuration and troubleshooting.
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Convert secondary indexes to the DocumentDB-compatible format — Option B is correct because Amazon DocumentDB does not support the same range of secondary indexes as MongoDB; converting indexes ensures performance. Option A is wrong because DocumentDB uses its own storage, not EBS. Option C is wrong because DynamoDB Accelerator is for DynamoDB, not DocumentDB. Option D is wrong because vertical scaling is often insufficient; proper indexing is key.
What should I do if I get this DBS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DBS-C01 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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