How Items Connect — The Decision Protocol

When you face an architectural decision, use this sequence:

1. Identify which tradeoff is in play. Name it from the ten. If you cannot name it, you have not understood the decision yet.
2. Establish what the requirement demands. Not what you prefer — what the requirement says. “We need P99 latency under 100ms” drives AT2. “We cannot lose a payment” drives AT1 and AT9.
3. Name the cost on the other side. If you choose consistency (AT1), you are accepting reduced availability. Name that cost explicitly. If the business cannot accept it, revisit the decision.
4. Record the decision and the tradeoff. Write an Architecture Decision Record (ADR). Future engineers need to know not just what was decided but what tradeoff was made and what would cause it to be revisited.