Migrating Amazon RDS for PostgreSQL to Amazon Aurora using seeded logical replication

This article explains how to migrate from Amazon RDS for PostgreSQL to Amazon Aurora PostgreSQL using seeded logical replication, addressing the critical LSN (log sequence number) divergence challenge.

• LSN divergence occurs because RDS and Aurora use fundamentally different transaction log architectures
• Extract seed LSN from temporary RDS instance restored from same snapshot as Aurora target
• Two migration options: Publisher-subscriber model or AWS DMS CDC-only task for ongoing replication
• Seeded logical replication enables hot standby Aurora cluster with multi-reader topology for load testing
• Monitor CloudWatch metrics (OldestReplicationSlotLag, ReplicationSlotDiskUsage, FreeStorageSpace) to prevent storage outages
• Logical replication doesn't replicate schema, DDL, large objects, or sequences
• Straightforward rollback available since source RDS remains fully operational throughout

This approach enables realistic production-like load testing on Aurora before cutover with zero read downtime and supports combined migration-upgrade scenarios.