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Difficulty: HardDesigning Migration Plans and Data Transfer Strategies

An enterprise logistics provider is migrating its core operational architecture from an on-premises data center to Google Cloud. The workload comprises a live 5 TB5\text{ TB} transactional PostgreSQL database migrating to Cloud SQL for PostgreSQL, along with 300 TB300\text{ TB} of unstructured document attachments migrating to Cloud Storage. The business demands continuous data replication with near-zero downtime during final cutover. Arrange the operational steps in the correct sequential order to execute this migration plan.

  1. 1Establish network connectivity via Dedicated Interconnect, launch Database Migration Service (DMS) in continuous CDC mode for PostgreSQL, and initiate initial transfer jobs using Storage Transfer Service.
  2. 2Monitor replication lag on DMS and execute periodic delta syncs with Storage Transfer Service until the target Cloud SQL database and Cloud Storage bucket reach near-real-time synchronization.
  3. 3Place the on-premises source database into read-only mode to freeze incoming write transactions, then trigger a final incremental sync run with Storage Transfer Service.
  4. 4Verify zero replication lag in DMS, promote the Cloud SQL target instance to a standalone primary database, and reconfigure application connection endpoints to GCP.
  5. 5Perform post-migration application integration health checks and resume full production write traffic on the newly promoted GCP environment.

Answer

The correct order of steps is: 1) Establish connectivity, start continuous DMS CDC, and launch Storage Transfer Service initial bulk transfer; 2) Monitor replication lag and run delta syncs until synchronization parity is reached; 3) Set source database to read-only mode and run final incremental file transfer; 4) Verify zero replication lag, promote Cloud SQL to standalone primary, and update application connection endpoints; 5) Complete health validation checks and open write traffic on Google Cloud.
The migration cutover must proceed in a logical sequence to minimize downtime and prevent data loss. Baseline connectivity and replication (DMS CDC + Storage Transfer Service) are established first while the source remains active. Next, replication lag is monitored until parity is achieved. To prevent data divergence, write traffic on the source database is stopped by putting it in read-only mode, followed by a final incremental file transfer. After verifying zero replication lag, the Cloud SQL target instance is promoted to a standalone primary database and connection endpoints are updated. Finally, post-migration health checks validate system integrity before resuming production write traffic on GCP.

Step-by-Step Solution

1
Establish connectivity and start baseline replication tools.
Continuous CDC streaming begins via DMS alongside baseline Storage Transfer Service object ingestion without interrupting live source writes.
Data transfer tools must establish baseline copies and streaming CDC while the on-premises application remains fully operational.
2
Track replication lag and perform incremental synchronization.
Target Cloud SQL and Cloud Storage environments reach continuous near-zero latency synchronization with source data.
Verifying sync parity guarantees that the cutover window can be kept as brief as possible.
3
Quiesce source writes and trigger final delta syncs.
On-premises state is frozen to guarantee consistency while final transactions flush across the pipeline.
Preventing new writes eliminates data divergence and ensures strict zero-data-loss cutover.
4
Promote target database instance and rebind endpoints.
Cloud SQL becomes a standalone primary write instance, and application connection strings are pointed to GCP services.
Promoting Cloud SQL converts it from a replication target to the active master database.
5
Validate deployment health and resume production writes.
System end-to-end functionality is confirmed and production operations resume cleanly on GCP.
Final validation verifies that all application endpoints and data stores behave correctly under load before live user writes begin.

Key Concept

Database migration staging, CDC continuous replication, and cutover sequencing using GCP Database Migration Service and Storage Transfer Service.
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Topics

Designing Migration Plans and Data Transfer Strategies