30. Observability
1
The picture to keep in your head2
30.1 Why do you need observability?3
30.2 What are the three pillars?4
30.3 What are golden signals, RED and USE?5
30.4 What are SLI, SLO and SLA?6
30.5 What are error budgets?7
30.6 How do you alert without noise?8
30.7 What makes a good dashboard?9
30.8 How do you debug an incident, step by step?10
Memory card and where the analogy breaks11
Practice: five levels12
Interview questions13
Solutions14
Sources15
Code lab30. Observability
Memory card and where the analogy breaks
3 min read+10 XP
The memory card (tear this page out)
| # | Question | Memory code |
|---|---|---|
| 30.1 | Why observability? | Plug in the reader before you open the engine |
| 30.2 | Three pillars (logs, metrics, traces)? | The log says what, the gauges say how much, the replay says where |
| 30.3 | Golden signals, RED, USE? | Speed, fuel, temperature, warnings: watch the few that tell you most |
| 30.4 | SLI, SLO, SLA? | Measure the kilometres, promise the service interval, sign the warranty looser |
| 30.5 | Error budgets? | The slack before the next service is yours to spend, but watch how fast you're spending it |
| 30.6 | Alerting without noise? | A warning light should mean "stop now", never "speed bump" |
| 30.7 | Dashboards? | Speedometer in front, trip computer one press away |
| 30.8 | Debugging an incident? | Pull over, read the gauges, find what changed, replay the trip, then fix and write it down |
The whole chapter in one line: Emit structured logs, metrics and traces linked by a trace ID, watch percentiles of what users feel, set SLOs with error budgets, page only on fast budget burn, and in an incident mitigate first, then break down by dimension and follow one bad request.
Where the analogy breaks
- A car has one driver and one engine. A request may cross twenty services, which is why traces need a shared ID passed along every call.
- Car gauges are free. Telemetry costs money, and logs especially can cost more than the servers they describe, so sample and choose.
- A car's warning lights are designed once at the factory. Alerts are yours to design, and bad ones get ignored until the day they matter.
Quick check
Five questions on this chapter. Pick an answer, then check it.
quiz