The correct approach is to use AWS Database Migration Service (AWS DMS) with ongoing replication from the MongoDB source. This method leverages DMS’s change data capture (CDC) capability, which reads the MongoDB oplog to continuously capture and apply changes to Amazon DocumentDB without locking the source database, ensuring minimal performance impact even on a 100 GB production workload. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of live migration strategies versus batch export/import methods, which would cause significant downtime and source strain. A common trap is choosing a full snapshot or mongodump, but DMS with ongoing replication allows near-zero downtime by keeping the target synchronized until cutover. Memory tip: “Oplog equals ongoing” — if you see “minimal downtime” and “MongoDB to DocumentDB,” think DMS with CDC reading the oplog.
DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 needs to migrate a 100 GB MongoDB database to Amazon DocumentDB (with MongoDB compatibility). The migration must have minimal impact on the source database performance. Which approach should the company take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS Database Migration Service (AWS DMS) with ongoing replication from the MongoDB source.
AWS DMS with ongoing replication is the correct approach because it supports continuous change data capture (CDC) from MongoDB, enabling a live migration with minimal performance impact on the source. DMS reads the MongoDB oplog to capture changes without locking the database, which is critical for a 100 GB production database. This allows the target DocumentDB to stay synchronized until cutover, reducing downtime and avoiding the need for a full export/import that would strain the source.
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.
✓
Use AWS Database Migration Service (AWS DMS) with ongoing replication from the MongoDB source.
Why this is correct
AWS DMS supports MongoDB as a source and can perform continuous replication with minimal impact.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use AWS DataSync to transfer the MongoDB data files.
Why it's wrong here
AWS DataSync is for file-based data, not for live database migration.
✗
Set up a MongoDB replica set on Amazon EC2 and promote it to primary, then migrate to DocumentDB.
Why it's wrong here
This adds complexity and does not directly migrate to DocumentDB; it's an intermediate step.
✗
Use mongodump to export the data and mongorestore to import into DocumentDB.
Why it's wrong here
Mongodump can impact source performance and may require downtime if consistency is needed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose mongodump/mongorestore (Option D) as the simplest tool, overlooking that it causes significant source performance impact and downtime for large databases, while AWS DMS's CDC capability is specifically designed for minimal-impact migrations.
Detailed technical explanation
How to think about this question
AWS DMS for MongoDB uses the MongoDB oplog (capped collection) to capture insert, update, and delete operations in real time, applying them to DocumentDB via its MongoDB-compatible API. The oplog size and retention must be configured to ensure DMS can catch up during the initial load; if the oplog wraps, DMS may fail, requiring a full reload. In practice, for databases over 50 GB, DMS's parallel load feature partitions the collection by document ID ranges to speed up the full load while CDC runs concurrently.
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 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. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Deployment and Migration — This question tests Deployment and Migration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use AWS Database Migration Service (AWS DMS) with ongoing replication from the MongoDB source. — AWS DMS with ongoing replication is the correct approach because it supports continuous change data capture (CDC) from MongoDB, enabling a live migration with minimal performance impact on the source. DMS reads the MongoDB oplog to capture changes without locking the database, which is critical for a 100 GB production database. This allows the target DocumentDB to stay synchronized until cutover, reducing downtime and avoiding the need for a full export/import that would strain the source.
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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating a 5 TB MongoDB database to Amazon DocumentDB. They have a short maintenance window and need to minimize downtime. Which migration strategy should be used?
hard
✓ A.Use AWS DMS to perform a full load and then ongoing replication from the source MongoDB.
B.Use the MongoDB change streams feature to replicate changes to DocumentDB in real time.
C.Set up AWS Direct Connect to the source and use mongorestore directly to DocumentDB.
D.Export the data using mongodump, transfer to Amazon S3, and import using mongorestore.
Why A: AWS DMS supports MongoDB as a source and Amazon DocumentDB as a target, enabling a full load of the 5 TB database followed by ongoing change data capture (CDC) using MongoDB's oplog. This minimizes downtime by keeping the target nearly synchronized during the migration window, allowing a final cutover with minimal interruption.
Variation 2. A company is migrating a MongoDB database to Amazon DocumentDB. They have a 200 GB database and need to minimize downtime. Which migration approach is most appropriate?
medium
A.Take an EBS snapshot of the MongoDB volume and restore it to DocumentDB.
✓ B.Set up MongoDB replication from the source to DocumentDB, then promote DocumentDB.
C.Export the database using mongodump and import using mongorestore into DocumentDB.
D.Use AWS DMS to migrate data from MongoDB to DocumentDB.
Why B: Option B is correct because DocumentDB supports MongoDB 3.6/4.0 replication protocol, allowing near-zero downtime via native replication. Option A is wrong because mongodump/mongorestore requires downtime. Option C is wrong because AWS DMS does not support MongoDB as a source. Option D is wrong because EBS snapshots are not applicable to DocumentDB.
Variation 3. A media company is migrating a 5 TB MongoDB database to Amazon DocumentDB. The migration must have minimal downtime. The source MongoDB uses sharding across 10 shards. Which migration strategy is MOST appropriate?
hard
A.Use native MongoDB replication to sync to DocumentDB
✓ B.Use AWS DMS with MongoDB as source and DocumentDB as target, enabling CDC
C.Export data to S3 and use AWS Glue to load into DocumentDB
D.Use mongoexport to export data and mongoimport to import into DocumentDB
Why B: Option B is correct because DocumentDB supports reading from MongoDB oplog for CDC, enabling minimal downtime. Option A is wrong because mongoexport/import is offline. Option C is wrong because S3 is not suitable for CDC. Option D is wrong because DMS does not support DocumentDB as a target.
Variation 4. A company wants to migrate an on-premises MongoDB database to Amazon DocumentDB. The migration should be performed with minimal application changes. Which AWS service should be used?
easy
A.Amazon S3 Transfer Acceleration
B.AWS DataSync
C.AWS Schema Conversion Tool (AWS SCT)
✓ D.AWS Database Migration Service (AWS DMS)
Why D: AWS DMS is the correct service because it supports homogeneous migrations from MongoDB to Amazon DocumentDB, including ongoing replication via change data capture (CDC) to minimize downtime. It handles schema conversion automatically for compatible data types, requiring minimal application changes since DocumentDB is MongoDB-compatible. AWS DMS can migrate data directly from a MongoDB source to a DocumentDB target without needing an intermediate schema transformation tool.
Variation 5. A company wants to migrate an on-premises MongoDB database to Amazon DocumentDB. The migration must be performed with minimal downtime and should support live data synchronization. Which AWS service should be used?
easy
A.AWS Glue with streaming ETL jobs.
B.AWS Data Pipeline to schedule periodic data loads.
C.AWS S3 with AWS Lambda functions to sync data.
✓ D.AWS Database Migration Service (DMS) with ongoing replication.
Why D: Option A is correct because AWS DMS supports MongoDB as a source and DocumentDB as a target, and can perform live synchronization. Option B is wrong because Data Pipeline is for data processing, not live migration. Option C is wrong because Glue is for ETL, not ongoing replication. Option D is wrong because S3 is for storage, not data replication.
Variation 6. A company is migrating a 10 TB MongoDB database to Amazon DocumentDB. The migration must have minimal downtime. Which strategy should be used?
hard
A.Use mongodump to export the database and mongorestore to import into DocumentDB.
B.Use AWS CloudEndure to replicate the MongoDB server to DocumentDB.
C.Copy the database files to Amazon S3 and restore to DocumentDB.
✓ D.Use AWS DMS with MongoDB as source and DocumentDB as target, with change data capture.
Why D: AWS DMS with MongoDB as source and DocumentDB as target, using change data capture (CDC), is the correct strategy because it enables a live migration with minimal downtime. DMS performs an initial full load of the 10 TB database and then continuously replicates ongoing changes from the MongoDB oplog, allowing you to cut over to DocumentDB with only a brief pause.
Variation 7. A company is migrating a 500 GB MongoDB database to Amazon DocumentDB. The migration must have minimal impact on the source database. Which approach should the company take?
medium
A.Use mongodump to export the data, then use mongorestore to import into DocumentDB.
B.Use mongoexport to export CSV, then use the DocumentDB import tool.
✓ C.Use AWS Database Migration Service (DMS) with MongoDB as source and DocumentDB as target.
D.Use AWS Schema Conversion Tool (SCT) to convert schema, then copy data.
Why C: AWS DMS supports MongoDB as a source and DocumentDB as a target, with ongoing replication to minimize downtime. Option A (mongorestore) causes high impact. Option C (export/import) causes impact. Option D (AWS SCT) is not for migration itself.
Variation 8. A company is migrating an on-premises MongoDB database to Amazon DocumentDB. The migration must be online with minimal downtime. The source MongoDB is version 4.0 and uses replica sets. Which tool should the company use?
hard
A.Use MongoDB Compass to export data and import into DocumentDB.
B.Use mongodump and mongorestore.
C.Create a read replica of the MongoDB replica set and promote to DocumentDB.
✓ D.Use AWS DMS with MongoDB as source and DocumentDB as target.
Why D: Option B is correct because AWS DMS supports MongoDB as a source and DocumentDB as a target, and can perform ongoing replication for minimal downtime. Option A is wrong because mongodump/mongorestore is a logical dump that requires downtime for a consistent snapshot. Option C is wrong because MongoDB Compass is a GUI tool and does not support ongoing replication to DocumentDB. Option D is wrong because creating a read replica from MongoDB to DocumentDB is not supported.
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