Observability vs. Monitoring: What's the Difference?

For years, monitoring has been the standard for tracking system health. But as systems become more complex and distributed, a new approach—observability—has become essential.

Monitoring: The Known Unknowns

Monitoring is about watching for pre-defined problems. You set up checks and dashboards for things you already know might go wrong:

• Is the server's CPU usage too high?
• Is the database responding?
• Is there enough disk space?

This is a "known unknowns" approach. You anticipate potential failure modes and create alerts for them. It's effective for predictable issues but falls short when unexpected problems arise.

Observability: The Unknown Unknowns

Observability, on the other hand, is about being able to answer questions you didn't know you needed to ask. It's about exploring your system's behavior to understand the root cause of novel problems—the "unknown unknowns."

An observable system is one that generates rich, detailed data about its internal state, built on three pillars:

• Metrics: Aggregated numerical data that tells you *what* is happening (e.g., request rates, error counts).
• Logs: Timestamped records of discrete events, providing context and detail.
• Traces: A detailed view of a single request or transaction as it moves through all the different services in your system.

With observability, you don't just get an alert that something is wrong; you get the data you need to ask why it's wrong, even if you've never seen that particular failure before. It's the difference between having a smoke alarm and having a full diagnostics toolkit.