The three pillars of a robust system: HA, reliability, and resiliency

Before we get into the details of how Kubernetes helps with high availability, reliability, and resiliency, it’s important to understand what these terms mean. We’ll start by defining what high availability means, how it differs from reliability and resiliency, and why these concepts are critical for any modern application running in a Kubernetes cluster.

What is high availability?

High availability (HA) means designing your system to stay operational even when parts of it fail. We measure it as a percentage of uptime per year. For example, a system with 99.9% availability has an expected downtime of just a few hours per year. The higher the availability, the more complex and resilient the system needs to be.

Here’s a table showing how much downtime is allowed per year depending on the percentage of availability:

Availability (%) ...