Bus factor

The bus factor is how exposed you are if key people, perhaps with critical knowledge or skills, were hit by a bus.

Examples might include the only people able to keep a company running, restore a server from a backup, or someone who held the only key to unlock crypto assets of its customers . As a result, many places are set up with, or required to have by investors or insurers, some redundancy — say two experienced developers with knowledge of how a service works — to minimise the risk of a tragic accident also being a severe problem for a company or its customers.

As a metaphor, the bus factor may be helpful to consider without the need for people to actually be hit by a bus. It may be worth thinking through how you might operate if someone was late, missed their flight, was ill on the day, or simply quit . In operational roles, this will often lead to a minimum of two people for each key position if nothing else to allow one to take a break from time to time.

An alternative framing, with fewer fatalities, is 'what if we all won the lottery?' and so decided to go do something else.