Right-Size AWS Transform MGN Replication Servers

This article presents an automated Lambda-based solution for right-sizing AWS Transform MGN replication servers based on source disk capacity during large-scale migrations.

• Lambda function evaluates provisioned source-disk capacity and maps servers to configurable replication-server instance tiers
• Supports dry-run mode for review before applying changes, with optional EventBridge scheduling for recurring evaluation
• Uses configurable size tiers (default: m5.xlarge to m5.12xlarge) based on disk capacity thresholds in GiB
• Deploys via two-phase Terraform: automation stack in deployment account, then target-account IAM role
• Includes safety controls: upgrade-only policy, per-server validation, reserved Lambda concurrency, and encrypted dead-letter queue for failed events
• Provides manual invocation, dry-run validation, and recovery procedures for failed updates

The solution automates repetitive replication-server configuration work while maintaining operator approval, cost control, and post-change validation throughout the migration wave.