The correct choice is to check if all aggregation pipeline stages used by the application are supported in DocumentDB. This is because Amazon DocumentDB, while offering MongoDB compatibility, does not implement every stage of MongoDB’s aggregation pipeline. Specifically, while `$lookup` and `$unwind` are supported, stages like `$merge`, `$facet`, `$bucket`, `$bucketAuto`, `$graphLookup`, and `$search` are not, so verifying each stage before migration prevents runtime failures. On the AWS Certified Database Specialty DBS-C01 exam, this question tests your understanding of DocumentDB’s feature parity limitations, often appearing as a trap where candidates assume full MongoDB compatibility. A common memory tip is to remember that DocumentDB supports the “core” pipeline stages for joining and reshaping documents, but not the advanced analytical or search-oriented stages. Think of it as “lookup and unwind are fine, but merge, facet, and graph are left behind.”
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 (with MongoDB compatibility). The application uses MongoDB's aggregation pipeline with $lookup and $unwind stages. What should the company verify before migration?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check if all aggregation pipeline stages used by the application are supported in DocumentDB.
Option A is correct because Amazon DocumentDB (with MongoDB compatibility) does not support all MongoDB aggregation pipeline stages. Specifically, the `$lookup` and `$unwind` stages are supported, but other stages like `$merge`, `$facet`, `$bucket`, `$bucketAuto`, `$graphLookup`, and `$search` are not. Before migration, the company must verify that every stage used in their application's aggregation pipelines is fully supported in DocumentDB to avoid runtime failures.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Check if all aggregation pipeline stages used by the application are supported in DocumentDB.
Why this is correct
DocumentDB has limitations on some aggregation stages; verifying compatibility is essential.
Related concept
Read the scenario before looking for a memorised answer.
✗
Verify that DocumentDB supports sharding for the collection.
Why it's wrong here
DocumentDB supports sharding, but not all MongoDB sharding features.
✗
Ensure the application uses the latest MongoDB driver.
Why it's wrong here
Driver compatibility is usually fine; the focus should be on feature parity.
✗
Confirm that the application's secondary indexes can be migrated.
Why it's wrong here
Secondary indexes are supported in DocumentDB; this is generally not an issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume DocumentDB is fully MongoDB-compatible and overlook the specific limitations in the aggregation pipeline, especially for advanced stages like `$facet` and `$graphLookup`, which are not supported.
Detailed technical explanation
How to think about this question
Under the hood, DocumentDB implements a subset of the MongoDB aggregation pipeline, focusing on commonly used stages like `$match`, `$group`, `$sort`, `$project`, `$lookup`, and `$unwind`. However, stages that require in-memory processing or complex data transformations (e.g., `$facet`, `$bucket`, `$graphLookup`) are not supported. A real-world scenario is a reporting application that uses `$facet` to generate multiple aggregations in a single query; this would fail in DocumentDB, requiring the pipeline to be broken into separate queries or rewritten.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Check if all aggregation pipeline stages used by the application are supported in DocumentDB. — Option A is correct because Amazon DocumentDB (with MongoDB compatibility) does not support all MongoDB aggregation pipeline stages. Specifically, the `$lookup` and `$unwind` stages are supported, but other stages like `$merge`, `$facet`, `$bucket`, `$bucketAuto`, `$graphLookup`, and `$search` are not. Before migration, the company must verify that every stage used in their application's aggregation pipelines is fully supported in DocumentDB to avoid runtime failures.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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