The DR plan that claims fifteen minutes

A documented disaster-recovery plan states an RTO of 15 minutes and an RPO of 5 minutes for a transactional web application. The architecture: an Auto Scaling group behind an ALB in eu-west-1, an RDS PostgreSQL instance with Multi-AZ enabled, an S3 bucket with cross-region replication to eu-central-1, and AMIs copied nightly to eu-central-1.

There is no compute running in eu-central-1. There is a cross-region read replica of the database, created two months ago. Route 53 uses a simple record pointing at the eu-west-1 ALB. DNS TTL is 300 seconds.

The plan has never been tested end to end.

Assume eu-west-1 becomes entirely unavailable. Walk me through what actually has to happen, estimate the real RTO and RPO with reasoning, and identify which single claim in that plan is most dangerously wrong.