You cannot debug what you did not instrument. Start earlier than feels reasonable.
Observe the first real workflow
Observability is not a reward for reaching high traffic. Small systems already fail across browsers, networks, integrations and background jobs. Logs, metrics and traces shorten the distance between a user report and an explanation.
Begin with critical user journeys. Record whether they start, complete and fail, then connect those signals with a request or correlation identifier.
Prefer useful signals
More telemetry is not automatically better. Capture structured events with consistent names, relevant context and clear retention. Avoid placing secrets or unnecessary personal information in logs.
Define service indicators for availability, latency, correctness and freshness. Alert on conditions that require action, not every unusual number.
Make response routine
Dashboards should answer operational questions, and alerts should link to ownership and a response procedure. Test that the team can locate a failure and understand its impact.
Review incidents to improve both the system and its signals. If an outage was visible to users before it was visible to the team, observability has a specific gap to close.