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.
Choose how you want to be interrogated
The same case under two modes is two different exercises. If you are unsure, RCA drill is the one that trains root-cause analysis most directly.
RCA drill
A symptom, and nothing else. Find the cause and prove it.
Trains: Hypothesis generation, ranking by prior, and naming the test that discriminates.
Red team
You propose. It attacks. It is trying to make you wrong.
Trains: Defending a position under pressure, and noticing when you should concede.
Socratic
Questions only. It will never tell you the answer.
Trains: Deriving from first principles instead of retrieving from memory.
Design review
Present an architecture. Justify every trade-off you made.
Trains: Stating what you optimised and what you gave up, on purpose.
Viva
Rapid escalating questions. Ends in a graded verdict.
Trains: Answering under time pressure without hedging.
Integration
Problems that span several domains at once. The hardest mode.
Trains: Reasoning across boundaries, where the cause is in a different system to the symptom.
Before you start: you begin locked. The Mentor will give you nothing — not a nudge, not a category — until you state a specific position and the mechanism you think produces it. Four genuine attempts unlock the resolution. There is no shortcut.