The correct approach is to use a custom application to capture MongoDB oplog changes and apply them to DocumentDB. This is necessary because Amazon DocumentDB, which is compatible with MongoDB 3.6, does not support the change streams feature introduced in MongoDB 4.0, making native replication impossible. The custom tool reads the source’s oplog—a capped collection recording all writes—and replays those operations on the target, enabling an online migration with minimal downtime. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of DocumentDB’s version limitations and the distinction between offline and online migration methods. A common trap is assuming AWS DMS can handle online migrations from MongoDB to DocumentDB, but DMS only supports offline full loads for this source-target pair. Another pitfall is expecting DocumentDB to have built-in replication from MongoDB 4.0, which it does not. Memory tip: “Oplog, not changelog”—when versions mismatch, fall back to the oplog-based custom tool for live sync.
DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. 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 a self-hosted MongoDB replica set to Amazon DocumentDB. The source MongoDB is version 4.0, and the target DocumentDB is 3.6. The migration must be online with minimal downtime. Which approach should be taken?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a custom application to capture MongoDB oplog changes and apply to DocumentDB.
Option D is correct because DocumentDB doesn't support change streams from MongoDB 4.0; using a custom replication tool is needed. Option A is wrong because DocumentDB has no native replication capability. Option B is wrong because DMS supports MongoDB to DocumentDB but only offline full load. Option C is wrong because it requires downtime.
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.
✗
Use AWS DMS with ongoing replication from MongoDB to DocumentDB.
Why it's wrong here
DMS does not support ongoing replication for DocumentDB target.
✓
Use a custom application to capture MongoDB oplog changes and apply to DocumentDB.
Why this is correct
Custom replication using oplog is a common approach for near-zero downtime.
Related concept
Static NAT maps one inside address to one outside address.
✗
Configure DocumentDB as a replica of the MongoDB primary.
Why it's wrong here
DocumentDB does not support replication from external MongoDB.
✗
Export MongoDB collection data to JSON files, then import into DocumentDB.
Why it's wrong here
Requires downtime.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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.
Deployment and Migration — This question tests Deployment and Migration — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use a custom application to capture MongoDB oplog changes and apply to DocumentDB. — Option D is correct because DocumentDB doesn't support change streams from MongoDB 4.0; using a custom replication tool is needed. Option A is wrong because DocumentDB has no native replication capability. Option B is wrong because DMS supports MongoDB to DocumentDB but only offline full load. Option C is wrong because it requires downtime.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This DBS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DBS-C01 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.