What is redundancy as a mental model?

It’s having backup capacity — spare parts, reserves, multiple pathways — so one component’s failure doesn’t collapse the whole system. It looks inefficient in calm times and proves essential under stress.

What is an example of redundancy?

The human body’s two kidneys and two lungs: you can survive losing one. Nature builds in apparent overkill everywhere because the cost of duplication is small next to the cost of total failure.

How is redundancy related to a margin of safety?

Both are buffers against failure. A margin of safety is slack between your estimate and disaster; redundancy is duplicated capacity so no single failure is fatal. Both trade apparent efficiency for resilience.

Redundancy

Engineering & risk

Redundancy is having backup capacity — spare parts, reserves, multiple pathways — so that the failure of one component doesn’t bring down the whole system. It looks inefficient in good times and proves essential in bad ones.

How it works

For anything you can’t afford to have fail, build in more than the minimum: a backup, a buffer, a second supplier, a cash reserve. Accept the apparent waste of duplicated capacity as the price of surviving the failures that single points of failure can’t.

How to use it

Avoiding single points of failure in systems, finances, supply chains, and plans.
Holding reserves (cash, time, energy) that look idle but absorb shocks.
Recognising that "efficient" systems with no slack are often the most fragile.

Worked example

The human body has two kidneys, two lungs, and far more liver than it needs — apparent overkill that lets you survive losing one. Nature builds in redundancy everywhere, because the cost of duplication is small next to the cost of total failure.

Where it fails

Redundancy costs money and looks wasteful, so it’s the first thing cut in the name of efficiency — usually right before the failure it would have absorbed. But too much is genuinely wasteful; the art is matching redundancy to the cost of failure.

The deeper point

It exposes the hidden cost of optimisation: a system tuned for perfect efficiency has, by definition, removed all its slack — which is exactly the slack that absorbs shocks. The waste you cut in good times is the survival you lack in bad ones.

Frequently asked

What is redundancy as a mental model?: It’s having backup capacity — spare parts, reserves, multiple pathways — so one component’s failure doesn’t collapse the whole system. It looks inefficient in calm times and proves essential under stress.
What is an example of redundancy?: The human body’s two kidneys and two lungs: you can survive losing one. Nature builds in apparent overkill everywhere because the cost of duplication is small next to the cost of total failure.
How is redundancy related to a margin of safety?: Both are buffers against failure. A margin of safety is slack between your estimate and disaster; redundancy is duplicated capacity so no single failure is fatal. Both trade apparent efficiency for resilience.

Margin of safety Antifragility Systems thinking

Editorial synthesis © ReadGlobe 2026, drawing on the mental-models tradition (Charlie Munger, Farnam Street) and the primary sources for each model. · Last reviewed 2026-05-29.