They enabled Multi-AZ to fix read load
An RDS PostgreSQL instance is CPU-saturated. Roughly 85% of the query volume is reads from a reporting dashboard; the remaining 15% is transactional writes from the application.
The team enabled Multi-AZ, reasoning that a second instance would share the load. Cost roughly doubled. CPU on the primary is unchanged. Dashboard queries are as slow as before.
They now propose enabling Multi-AZ in a second Region as well.
Explain precisely why Multi-AZ changed nothing about the symptom, what they should have done instead, and what the correct fix is given that 85% of load is reporting queries.
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.