False definition of reliability

“By definition, reliability is the probability a system will fail in a given period.”

This is wrong. It’s 1 minus that number.

Course: Grokking the System Design Interview - Learn Interactively
Lesson: Key Characteristics of Distributed Systems - Grokking the System Design Interview

Hi @Sam, Thank you for contacting us.

Reliability is the ability of the system to function without failure. In simple words, a reliable system will perform its intended tasks without any failure or collapse. If there is any probability that a system will fail at any given time or at any condition, then that system is less reliable, and if there is a higher probability that the system will perform all of its intended tasks successfully, then it is more reliable. The statement in the lesson is not mathematical that is why the author has tried to explain it in simple words.