sre
4 free lessons tagged sre across Programming. Each one is a short sequence of focused steps with narration and a five-question quiz at the end — take them in any order, no signup required.
SLOs and Error Budgets: Turning Reliability Into a Number
How reliable should the service be? Wrong question: the right one is how much unreliability you can afford, spent deliberately. This lesson builds the SLI, SLO and error budget machinery from Google's SRE practice, does the arithmetic of nines, explains burn-rate alerting, and shows why 100 percent is the wrong target.
Distributed Tracing and the Art of Throwing Data Away
Tracing every request through every service produces the most useful telemetry you have and more of it than anyone can afford. This lesson covers how context propagation actually stitches a trace together, the head versus tail sampling decision and why it determines which incidents you can debug, and the collector pipeline where all of it is enforced.
Percentiles and Cardinality: The Two Numbers That Run Your Bill
Two pieces of arithmetic decide whether your telemetry is useful and affordable. Percentiles, because averages hide exactly the users who are suffering, and you cannot average a p99. Cardinality, because metric cost is not per event but per label combination, and one careless label can multiply your bill by the size of your user base. This lesson does both mechanisms by hand.
Metrics, Logs, Traces: Three Signals, Three Cost Models
Observability is not a product you buy but a property your system has: can you explain a behaviour you did not predict? This lesson defines the three telemetry signals, what question each answers, why their costs grow along completely different axes, and why the difference between monitoring and observability is the difference between known and unknown failure modes.