Grafana (LGTM)

Dashboards over any backend, plus Loki, Tempo, and Mimir for logs, traces, and metrics

Grafana began as a visualisation layer over other people's data and grew into the LGTM stack: Loki for logs, Grafana for dashboards, Tempo for traces and Mimir for long-term metrics. Interviews usually probe the boundary between those pieces. The most distinctive design decision is Loki's: it indexes only labels, not log content, which makes ingestion cheap and full-text search comparatively expensive — the opposite trade-off to Elasticsearch. Expect questions on when that trade-off is right and when it is not. On the dashboard side, questions tend to be about template variables, mixed data sources on one panel, and how to build a dashboard someone can actually use during an incident rather than one that looks impressive in a demo. Tempo's exemplar links, which jump from a metric spike straight to a representative trace, are a common follow-up.