How to migrate RDS Postgres to AWS Aurora without downtime?

Migrating from RDS Postgres to AWS Aurora without downtime can be achieved by using Amazon’s Database Migration Service (AWS DMS) along with additional strategies for minimizing the impact on production systems. Here’s a general outline of the steps you would take:

  1. Create an Aurora Read Replica: If your source database is running on Amazon RDS for PostgreSQL, you can create an Aurora Read Replica of the PostgreSQL DB instance. This is a straightforward process that can be done through the AWS Management Console. The replica will stay in sync with the source database until you’re ready to cut over.
  2. Promote the Read Replica: Once the data is in sync and you are ready to migrate, promote the Aurora Read Replica to a standalone Aurora DB cluster. This process will break the replication link with the source RDS instance and allow the Aurora cluster to accept write operations.
  3. Test the New Environment: Before cutting over your production traffic, thoroughly test the Aurora cluster to ensure that it performs as expected. This includes checking application compatibility, performance testing, and verifying that all data has been accurately replicated.
  4. Cutover to Aurora: After testing, you can cutover your application to the new Aurora cluster. This typically involves updating your application’s database connection strings to the endpoints of the Aurora cluster. The cutover should be planned during a period of low activity to minimize impact, even though the actual downtime can be just the time needed to redirect the connections from RDS to Aurora.
  5. Monitor After Migration: Once the migration is complete, continue to monitor the Aurora cluster closely to ensure that it operates as expected under normal load conditions.

For detailed instructions and considerations, you can refer to the AWS documentation on migrating data to Amazon Aurora with PostgreSQL compatibility. Remember that while the goal is to minimize downtime, the actual migration process may still involve brief periods where the database is read-only or otherwise not fully operational, depending on your specific setup and the size of your database.

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