Question 191 of 1,663
How to Migrate PostgreSQL to Amazon RDS with Minimal Downtime Using DMS CDC
A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database is 2 TB in size and has a high write workload. The company needs to minimize downtime during the migration. Which AWS service or feature should the company use to achieve this?
Quick Answer
The correct choice is AWS Database Migration Service (DMS) with ongoing replication, also known as change data capture (CDC). This approach is essential for migrating a 2 TB PostgreSQL database with a high write workload to Amazon RDS with minimal downtime because DMS first performs a full load of the existing data, then continuously captures and applies incremental changes from the source to the target. This keeps the target RDS instance synchronized right up to the cutover moment, allowing you to switch applications with only a brief pause. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of CDC as the key differentiator for minimizing downtime in large, write-heavy migrations. A common trap is selecting a one-time snapshot or backup restore, which would cause significant data loss or extended downtime. Remember the memory tip: “CDC keeps the clock ticking” — it’s the ongoing replication that makes the cutover nearly seamless.
⚠ Common exam trap
Watch out — candidates often confuse AWS DMS with AWS SCT, assuming SCT is needed for same-engine migrations, but SCT is only required for heterogeneous migrations, not for PostgreSQL to RDS PostgreSQL.
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 AWS Database Migration Service (AWS DMS) with ongoing replication.
AWS DMS with ongoing replication (change data capture, CDC) is the correct choice because it allows continuous synchronization of the source PostgreSQL database with the target RDS for PostgreSQL instance after an initial full load. This minimizes downtime by enabling the target to stay up-to-date with changes until the cutover, which is critical for a 2 TB database with a high write workload.
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 pg_dump and pg_restore to export and import the database.
Why it's wrong here
pg_dump/pg_restore requires the source database to be read-only during the dump, causing downtime.
- ✓
Use AWS Database Migration Service (AWS DMS) with ongoing replication.
Why this is correct
AWS DMS supports ongoing replication via change data capture, minimizing downtime.
- ✗
Use the AWS Schema Conversion Tool (AWS SCT) to convert the schema and migrate data.
Why it's wrong here
AWS SCT is primarily for schema conversion, not for minimizing downtime during data migration.
- ✗
Use AWS DataSync to replicate the database files.
Why it's wrong here
AWS DataSync is designed for file-based data transfers, not for live database migration with minimal downtime.
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Same concept, more angles
4 more ways this is tested on DBS-C01
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 an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database is 2 TB in size and has a high write volume. The migration window is limited to 4 hours. Which migration approach provides the fastest initial load with minimal downtime?
medium- A.Use pg_dump to export the database and pg_restore to import into RDS.
- B.Create a read replica of the on-premises database and promote it to a standalone database in RDS.
- C.Use AWS Schema Conversion Tool (AWS SCT) to convert the schema and then use AWS DMS for ongoing replication.
- ✓ D.Use AWS DMS with PostgreSQL as source and target, using native logical replication for full load and ongoing replication.
Why D: AWS DMS with native logical replication (using PostgreSQL's built-in logical replication slots) performs a full load of the 2 TB database while simultaneously capturing ongoing changes, enabling near-zero downtime during the migration window. This approach is optimized for high-write volumes and limited windows, as it avoids the need for a separate export/import step and minimizes the time the source database is unavailable.
Variation 2. A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database is 2 TB and has a sustained write rate of 150 MB/s. The migration must have minimal downtime. Which AWS service or tool should be used for the initial data load and ongoing replication?
medium- ✓ A.Use AWS Database Migration Service (AWS DMS) with full load and ongoing replication
- B.Use pg_dump and pg_restore
- C.Use AWS Schema Conversion Tool (AWS SCT) to convert schema and AWS DMS for data migration
- D.Use AWS S3 Transfer Acceleration to upload data to Amazon S3, then restore to RDS
Why A: AWS DMS is the correct choice because it supports both a full load of the existing 2 TB database and ongoing change data capture (CDC) to replicate transactions with minimal downtime. DMS can handle sustained write rates of 150 MB/s by using appropriate instance sizing and tuning, and it provides built-in mechanisms for resumable loads and validation, which are critical for a large-scale migration with minimal downtime.
Variation 3. A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database is 2 TB in size and has a sustained write rate of 50 MB/s. The migration must have minimal downtime. Which migration approach should be used?
medium- A.Create an RDS read replica from the on-premises database
- B.Use pg_dump and pg_restore
- C.Use AWS DMS with a full-load task only
- ✓ D.Use AWS DMS with ongoing replication (change data capture)
Why D: AWS DMS with ongoing replication (change data capture) is the correct approach because it allows a full load of the 2 TB database followed by continuous replication of changes from the on-premises PostgreSQL source to the RDS for PostgreSQL target, minimizing downtime to a brief cutover window. The sustained 50 MB/s write rate indicates a high-volume transactional workload that cannot be captured by a single full-load task, making CDC essential for near-zero downtime migration.
Variation 4. A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database is 2 TB and the migration must have minimal downtime. Which TWO AWS services should be used together to accomplish this?
medium- A.AWS CloudFormation
- B.AWS DataSync
- ✓ C.AWS Schema Conversion Tool (AWS SCT)
- D.AWS CloudEndure Migration
- ✓ E.AWS Database Migration Service (AWS DMS)
Why C: AWS Schema Conversion Tool (AWS SCT) is used to convert the source PostgreSQL schema and objects to be compatible with Amazon RDS for PostgreSQL, handling any heterogenous elements. AWS Database Migration Service (AWS DMS) then performs the continuous data replication from the on-premises database to RDS, enabling minimal downtime by keeping the target in sync until a cutover.
Last reviewed: Jun 11, 2026
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