Comcast Interview Question

How to provide a 100% SLA uptime problem with a distributed content delivery system?

Interview Answer

Anonymous

Dec 1, 2016

Mathematically explained why it was impossible and why every service including Azure, Amazon EC2, and other's offer 99.9% to 99.999% (Five 9's). The gentlemen in charge of the whole technology division had never heard of Five 9s of availability and felt that if it hasn't failed yet, then it meets 100% SLA. This is obviously incorrect and not how statistics nor Service-Level Agreements work.