Failure is inevitable: hard disks, networks, power, and so on all fail from time to time. But failures do not have to affect the users of your system.
A fault-tolerant system provides the highest quality to your users. No matter what happens in your system, the user is never affected and can continue to go about their work, consume entertaining content, buy goods and services, or have conversations with friends. A few years ago, achieving fault tolerance was expensive and complicated, but with AWS, providing fault-tolerant systems is becoming an affordable standard. Nevertheless, building fault-tolerant systems is the top tier of cloud computing and might be challenging at the beginning.