Before any system goes to production, ask:
| Q | Topic | Question |
|---|---|---|
| Q1 | Scale | What breaks at 10×? |
| Q2 | Failure | What happens when X is unavailable or slow? |
| Q3 | State | Where is the state? Who owns it? What is consistent? |
| Q4 | Latency | What is the critical path? What is the P99 budget? |
| Q5 | Evolution | Can the schema change without downtime? |
| Q6 | Security | What does an attacker gain if this component is compromised? |
| Q7 | Observe | Can you identify the root cause of a P1 in 15 minutes? |
| Q8* | Cost | What does this cost at 10× current scale? |
These cards are designed to be printed at A4 and taped near your monitor, or photographed and kept on your phone for pre-meeting review. The value is not in the cards themselves — it is in the retrievability they represent. When you can scan any card in 20 seconds and have it trigger full recall, you have reached the goal of this book.