Summary

In this chapter, you have discovered how to deploy highly available architectures on the AWS cloud. High-availability systems are trustworthy because they keep running even if some parts break. These systems are also robust, meaning they can absorb shocks to their operation without damaging their functionality and quickly and easily recover after experiencing a setback. The percentage of available time is a standard metric for gauging availability at a high level. The number of nines is often used as an indicator of extreme availability. An uptime of “four nines,” for instance, indicates that the system is available 99.99% of the time and has no more than 1 hour of downtime annually.

While load balancers offer the ability to build highly available systems, Auto Scaling is a service that enables you to design elasticity for your application. As demand for your application increases, AWS Auto Scaling can rapidly accommodate by deploying additional EC2 instances...