Question 1

What is the difference between monitoring and observability?

Accepted Answer

Monitoring watches known things: dashboards and alerts for metrics you decided in advance, like CPU or error rate. Observability is how well you can understand what is happening inside a system from its outputs, especially for problems you did not expect. It uses three main signals: metrics (numbers over time), logs (events) and traces (the path of one request through services).

Question 2

What would you monitor for a web application?

Accepted Answer

I start with the golden signals: latency (how long requests take), traffic (requests per second), errors (the rate of failed requests) and saturation (how full CPU, memory, disk or connections are). I add infrastructure metrics like node health, business metrics like sign-ups or orders, uptime checks from outside, and logs with request IDs so I can follow a problem.

Question 3

What are Prometheus and Grafana?

Accepted Answer

Prometheus is an open-source monitoring tool that scrapes metrics from apps and exporters every few seconds, stores them as time series and lets you query them with PromQL. Alertmanager sends its alerts to Slack, email or PagerDuty. Grafana is a dashboard tool that shows the data from Prometheus and other sources in graphs. Together they are the most common monitoring stack for Kubernetes.

Question 4

What makes a good alert?

Accepted Answer

A good alert means a real user-facing problem that a person must act on now, and it says what is wrong, how bad it is and links to a runbook. I alert on symptoms like a high error rate or slow responses, not every cause like CPU at 80%. Too many noisy alerts lead to alert fatigue and people start ignoring them. Less urgent problems go to a ticket or dashboard instead of waking someone up.

Question 5

What are SLI, SLO and SLA?

Accepted Answer

An SLI is a measurement, for example the percentage of requests that succeed in under 300 ms. An SLO is the internal target for it, like 99.9% over 30 days. An SLA is a contract with customers that may include penalties, and is usually looser than the SLO. The gap between 100% and the SLO is the error budget. If we use it up, we slow down releases and focus on reliability.

Monitoring interview questions