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LGTM Stack Explained

LGTM Stack Explained



The LGTM stack is a popular open-source observability stack maintained by Grafana Labs. It is designed to collect, store, and visualize logs, metrics, and traces in a unified way.



LGTM stands for:

  • Loki – Logs

  • Grafana – Visualization and dashboards

  • Tempo – Distributed tracing

  • Mimir – Long-term metrics storage

Together, these tools provide a complete observability solution that many teams use as an alternative to heavier or more expensive platforms.

Loki

Loki is a log aggregation system inspired by Prometheus.
Unlike traditional logging systems, Loki indexes only metadata (labels) instead of the full log content. This makes it much more cost-efficient and easier to operate.

Key characteristics:

  • Label-based indexing

  • Horizontal scalability

  • Low resource usage compared to Elasticsearch

  • Native integration with Grafana

Loki is commonly used to store application logs, system logs, and container logs.

Grafana

Grafana is the visualization and exploration layer of the stack.
It connects to Loki, Tempo, Mimir, and many other data sources to create dashboards, alerts, and exploratory views.

With Grafana you can:

  • Build dashboards for logs, metrics, and traces

  • Correlate logs with traces and metrics

  • Set up alerting rules

  • Create unified observability views

Grafana acts as the single pane of glass for the entire LGTM stack.

Tempo

Tempo is a distributed tracing backend.
It stores traces at high scale with minimal indexing, making it efficient and cost-effective.

Tempo works well with:

  • OpenTelemetry

  • Jaeger

  • Zipkin

It allows developers to follow requests across microservices and understand latency and failures.

Mimir

Mimir is a highly scalable, long-term storage system for Prometheus metrics.
It is designed for large multi-tenant environments and can handle high cardinality metrics reliably.

Mimir is often used when teams outgrow a single Prometheus instance and need durable, scalable metrics storage.

Why Teams Choose the LGTM Stack

  • Fully open source

  • Cost-efficient compared to traditional ELK or commercial APM tools

  • Strong integration between logs, metrics, and traces

  • Scales from small projects to large production systems

  • Active development and large community

Typical Architecture

Applications and infrastructure send:

  • Logs → Loki

  • Traces → Tempo

  • Metrics → Mimir (or Prometheus)

Grafana sits on top and provides a unified interface to query and visualize all three signals.

Conclusion

The LGTM stack offers a modern, efficient, and unified approach to observability. By combining Loki for logs, Tempo for traces, Mimir for metrics, and Grafana for visualization, teams can build a powerful monitoring system without relying on heavy or expensive proprietary platforms.

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