Alex Bramley talks to Sven Johann about the basics of service level objectives. They begin with terminologies (SLI, SLO, SLA, Error Budget), look at costs of outages and discuss what reliability has to do with customer happiness. They continue with having 100% reliability is the wrong target and what’s possibly the right target. Alex then explains how to get started with collecting data about your system’s behaviour. They close the first part of this series by looking into latency SLIs.