The Unstoppable Web

A feature needs two services, and both must be up for it to work. Compared with each service alone, the feature's uptime is:

• Higher, because there are two services
• Lower, because a failure of either one stops it
• The same as the better of the two

A writer publishes the same posts to three relays. When can readers not find a post?

• When any one relay is down
• When two of the three are down
• Only when all three are down at once