We now know how to examine our applications in Kubernetes. However, we are not yet confident enough to answer more complex questions, such as how healthy our application is, what changes have been made to the CPU usage from the new patch, when our databases will run out of capacity, and why our site rejects any requests. We therefore need a monitoring system to collect metrics from various sources, store and analyze the data received, and then respond to exceptions. In a classical setup of a monitoring system, we would gather metrics from at least three different sources to measure our service's availability, as well as its quality.