Margin of Safety

Core rule: commit a buffered number when residual uncertainty plus breach cost can cause ruin or costly failure. Margin covers estimation error; it is not free slack for laziness.

When to Use

• Capacity, timeouts, pool sizes, queue depths, storage, or SLA numbers under load uncertainty
• Timeline or budget commitments where underestimation is costly
• Architecture headroom when scaling or recovery is slow
• Any public or production commitment where being wrong has asymmetric downside

When NOT to Use

• Breach is detected immediately and fixed near-zero cost (fast auto-scale, live-tunable limit)—static fat buffers waste resources
• cost(buffer) > P(breach) × cost(breach)—right-size or measure instead of maxing out
• Uncertainty is eliminable by measurement or lookup—get the real number first
• Stopping-criterion / search budget problems—use bounded rationality, not padding
• Fully known parameters and low stakes where edge optimization is the goal